css

http://www.runoob.com/css/css-tutorial.html

字体(Font)

1. css中浏览器默认字体大小是16px .为了避免Internet Explorer 中无法调整文本的问题，许多开发者使用 em 单位代替像素。em的尺寸单位由W3C建议。 
   1em和当前字体大小相等。

链接

当设置为若干链路状态的样式，也有一些顺序规则： 
a:hover 必须跟在 a:link 和 a:visited后面 
a:active 必须跟在 a:hover后面

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:link</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">text-decoration</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">none</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:visited</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">text-decoration</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">none</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:hover</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">text-decoration</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">underline</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:active</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">text-decoration</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">underline</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

列表

不同列表项标记

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">ul</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.a</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">list-style-type</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> circle</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">ul</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.b</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">list-style-type</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> square</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">ol</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.c</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">list-style-type</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> upper-roman</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">ol</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.d</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">list-style-type</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> lower-alpha</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

要指定列表项标记的图像，使用列表样式图像属性： 
实例:

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">ul</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">list-style-image</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> <span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'sqpurple.gif'</span>)</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

框模型

 
不同部分的说明： 
- Margin - 清除边框区域。Margin没有背景颜色，它是完全透明 
- Border - 边框周围的填充和内容。边框是受到盒子的背景颜色影响 
- Padding - 清除内容周围的区域。会受到框中填充的背景颜色影响 
- Content - 盒子的内容，显示文本和图像

最终元素的总宽度计算公式是这样的： 
总元素的宽度=宽度+左填充+右填充+左边框+右边框+左边距+右边距 
元素的总高度最终计算公式是这样的： 
总元素的高度=高度+顶部填充+底部填充+上边框+下边框+上边距+下边距

CSS 分组 和 嵌套 选择器

在样式表中有很多具有相同样式的元素。

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">h1</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">green</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">h2</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">green</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">green</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>

为了尽量减少代码，你可以使用分组选择器。 
每个选择器用逗号分隔. 
在下面的例子中，我们对以上代码使用分组选择器： 
实例

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">h1</span>,<span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">h2</span>,<span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">green</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

嵌套选择器 
它可能适用于选择器内部的选择器的样式。 
在下面的例子，为所有p元素指定一个样式，为所有元素指定一个class=”marked”的样式，并仅用于class=”标记”，类内的p元素指定第三个样式： 
实例

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">blue</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">text-align</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">center</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.marked</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background-color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">red</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.marked</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">color</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">white</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

CSS Display(显示) 与 Visibility（可见性）

display属性设置一个元素应如何显示，visibility属性指定一个元素应可见还是隐藏。

隐藏元素 - display:none或visibility:hidden 
隐藏一个元素可以通过把display属性设置为”none”，或把visibility属性设置为”hidden”。但是请注意，这两种方法会产生不同的结果。 
visibility:hidden可以隐藏某个元素，但隐藏的元素仍需占用与未隐藏之前一样的空间。也就是说，该元素虽然被隐藏了，但仍然会影响布局。

CSS Display 块和内联元素 
块元素是一个元素，占用了全部宽度，在前后都是换行符。 
块元素的例子：

<code class="hljs haml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">-<span class="ruby" style="box-sizing: border-box;"> <<span class="hljs-constant" style="box-sizing: border-box;">H1</span>></span>-<span class="ruby" style="box-sizing: border-box;"> <<span class="hljs-constant" style="box-sizing: border-box;">P</span>></span>-<span class="ruby" style="box-sizing: border-box;"> <<span class="hljs-constant" style="box-sizing: border-box;">DIV</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

内联元素只需要必要的宽度，不强制换行。 
内联元素的例子：

<code class="hljs haml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">-<span class="ruby" style="box-sizing: border-box;"> <span></span>-<span class="ruby" style="box-sizing: border-box;"> <a></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

CSS Float(浮动)

什么是 CSS Float（浮动）？ 
CSS 的 Float（浮动），会使元素向左或向右移动，其周围的元素也会重新排列。 
Float（浮动），往往是用于图像，但它在布局时一样非常有用。

元素怎样浮动

元素的水平方向浮动，意味着元素只能左右移动而不能上下移动。 
一个浮动元素会尽量向左或向右移动，直到它的外边缘碰到包含框或另一个浮动框的边框为止。 
浮动元素之后的元素将围绕它。 
浮动元素之前的元素将不会受到影响。 
如果图像是右浮动，下面的文本流将环绕在它左边：

彼此相邻的浮动元素

如果你把几个浮动的元素放到一起，如果有空间的话，它们将彼此相邻。 
在这里，我们对图片廊使用 float 属性

清除浮动 - 使用 clear

元素浮动之后，周围的元素会重新排列，为了避免这种情况，使用 clear 属性。 
clear 属性指定元素两侧不能出现浮动元素。 
使用 clear 属性往文本中添加图片廊：

CSS 组合选择符

这个还是看例子吧 
访问:http://www.runoob.com/css/css-combinators.html

伪类伪元素

是用来添加一些选择器的特殊效果 
参考: css伪元素 
伪类

导航栏

• 垂直导航栏 
  上面的代码，我们只需要 元素的样式，建立一个垂直的导航栏：

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">display</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">block</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">width</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">60</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

示例说明： 
display:block - 显示块元素的链接，让整体变为可点击链接区域（不只是文本），它允许我们指定宽度 
width:60px - 块元素默认情况下是最大宽度。我们要指定一个60像素的宽度

• 水平导航栏 
  有两种方法创建横向导航栏。使用内联或浮动的列表项。 
  这两种方法都很好，但如果你想链接到具有相同的大小，你必须使用浮动的方法。 
  内嵌列表项 
  建立一个横向导航栏的方法之一是指定 
  元素， 上述代码是标准的内嵌:

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">li</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">display</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">inline</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

splay:inline; -默认情况下，

元素是块元素。在这里，我们删除换行符之前和之后每个列表项，以显示一行 。 
浮动列表项 
在上面的例子中链接有不同的宽度。 
对于所有的链接宽度相等，浮动

元素，并指定为 元素的宽度：

<code class="hljs css has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">li</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">float</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">left</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">display</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">block</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">width</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">60</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

CSS 图像透明/不透明

CSS Opacity 属性是W3C的CSS3建议的一部分。 
IE9，Firefox，Chrome，Opera，和Safari浏览器使用透明度属性可以将图像变的不透明。 Opacity属性值从0.0 - 1.0。值越小，使得元素更加透明。 
IE8和早期版本使用滤镜：alpha（opacity= x）。 x可以采取的值是从0 - 100。较低的值，使得元素更加透明。

图像拼合技术

• 图像拼合 
  图像拼合就是单个图像的集合。 
  有许多图像的网页可能需要很长的时间来加载和生成多个服务器的请求。 
  使用图像拼合会降低服务器的请求数量，并节省带宽.通过定义单个图像距离左边框和顶部的位置来展示需要的那 
  部分图像.

• 图像拼合+悬停效果 
  实例:

<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-doctype" style="color: rgb(102, 0, 102); box-sizing: border-box;"><!DOCTYPE html></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">html</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">head</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">style</span>></span><span class="css" style="box-sizing: border-box;"><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#navlist</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">position</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">relative</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#navlist</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">li</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">margin</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">0</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">padding</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">0</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">list-style</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">none</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">position</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">absolute</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">top</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">0</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#navlist</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">li</span>, <span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#navlist</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">height</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">44</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">display</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">block</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#home</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">left</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">0</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">width</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">46</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#home</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'img_navsprites_hover.gif'</span>)</span> <span class="hljs-number" style="box-sizing: border-box;">0</span> <span class="hljs-number" style="box-sizing: border-box;">0</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#home</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:hover</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> <span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'img_navsprites_hover.gif'</span>)</span> <span class="hljs-number" style="box-sizing: border-box;">0</span> -<span class="hljs-number" style="box-sizing: border-box;">45</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#prev</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">left</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">63</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">width</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">43</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#prev</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'img_navsprites_hover.gif'</span>)</span> -<span class="hljs-number" style="box-sizing: border-box;">47</span>px <span class="hljs-number" style="box-sizing: border-box;">0</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#prev</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:hover</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> <span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'img_navsprites_hover.gif'</span>)</span> -<span class="hljs-number" style="box-sizing: border-box;">47</span>px -<span class="hljs-number" style="box-sizing: border-box;">45</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#next</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">left</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">129</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">width</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">43</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#next</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'img_navsprites_hover.gif'</span>)</span> -<span class="hljs-number" style="box-sizing: border-box;">91</span>px <span class="hljs-number" style="box-sizing: border-box;">0</span></span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span><span class="hljs-id" style="box-sizing: border-box; color: rgb(155, 112, 63);">#next</span> <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">a</span><span class="hljs-pseudo" style="color: rgb(0, 0, 0); box-sizing: border-box;">:hover</span><span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">background</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"> <span class="hljs-function" style="box-sizing: border-box;">url(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'img_navsprites_hover.gif'</span>)</span> -<span class="hljs-number" style="box-sizing: border-box;">91</span>px -<span class="hljs-number" style="box-sizing: border-box;">45</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">style</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">head</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">body</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">ul</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"navlist"</span>></span>  <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">li</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"home"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">a</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">href</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"default.asp"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">a</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">li</span>></span>  <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">li</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"prev"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">a</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">href</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"css_intro.asp"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">a</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">li</span>></span>  <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">li</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">id</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"next"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">a</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">href</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"css_syntax.asp"</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">a</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">li</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">ul</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">body</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">html</span>></span>         </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul>

 
实例解析： 
由于该列表项包含一个链接，我们可以使用：hover伪类 
home a:hover{background: transparent url(img_navsprites_hover.gif) 0 -45px;} - 对于所有三个悬停图像，我们指定相同的背景位置，只是每个再向下45px

这个拼合图像由六个小图像组成的,上方的小图像向下移动45像素后与下方相同位置的图像正好重合,这样就形成了似乎是颜色暗黑的效果,好神奇啊!

CSS媒体类型

媒体类型允许你指定文件将如何在不同媒体呈现。该文件可以以不同的方式显示在屏幕上，在纸张上，或听觉浏览器等等。 
媒体类型 
一些CSS属性只设计了某些媒体。例如”voice-family”属性是专为听觉用户代理。其他一些属性可用于不同的媒体类型。例如，”font-size”属性可用于屏幕和印刷媒体，但有不同的值。屏幕和纸上的文件不同，通常需要一个更大的字体，sans - serif字体比较适合在屏幕上阅读，而serif字体更容易在纸上阅读。 
@media 规则 
@media 规则允许在相同样式表为不同媒体设置不同的样式。 
在下面的例子告诉我们浏览器屏幕上显示一个14像素的Verdana字体样式。但是如果页面打印，将是10个像素的Times字体。请注意，font-weight在屏幕上和纸上设置为粗体： 
实例:

<code class="hljs xml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">html</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">head</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">style</span>></span><span class="css" style="box-sizing: border-box;"><span class="hljs-at_rule" style="box-sizing: border-box;">@<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">media</span> screen  </span>{  <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.test</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">font-family</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">verdana,sans-serif</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">font-size</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">14</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span>  }<span class="hljs-at_rule" style="box-sizing: border-box;">@<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">media</span> print  </span>{  <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.test</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">font-family</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">times,serif</span></span>;<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">font-size</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);"><span class="hljs-number" style="box-sizing: border-box;">10</span>px</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span>  }<span class="hljs-at_rule" style="box-sizing: border-box;">@<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">media</span> screen,print  </span>{  <span class="hljs-tag" style="color: rgb(0, 0, 0); box-sizing: border-box;">p</span><span class="hljs-class" style="box-sizing: border-box; color: rgb(155, 112, 63);">.test</span> <span class="hljs-rules" style="box-sizing: border-box;">{<span class="hljs-rule" style="box-sizing: border-box;"><span class="hljs-attribute" style="box-sizing: border-box;">font-weight</span>:<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 102, 102);">bold</span></span>;<span class="hljs-rule" style="box-sizing: border-box;">}</span></span>  }</span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">style</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">head</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">body</span>></span>....<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">body</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">html</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>

CSS 属性选择器

具有特定属性的HTML元素样式 
具有特定属性的HTML元素样式不仅仅是class和id。 
还可以使用[属性 ~=|]