css loading

<style type="text/css">.test {position: relative;            width: 200px;            height: 200px;            margin: 100px;            border: 10px solid #f00;        } .test-loading-img {            background: url(Css/Themes/Default/Images/ajax-loader.gif) no-repeat;            top: 0px;            left: 0px;            right: 0px;            bottom: 0px;            margin: 0px;            width: inherit;            height: inherit;            position: absolute;            background-position-x: 50%;            background-position-y: 50%;            background-color: #000;            opacity: 0.6;        }</style><div id="dd" class="test">        <div>数据内容省略</div>        <div class="test-loading-img"></div></div>