判断IE的各个不同版本

<!--[if lte IE 6]>
<script src="js/iepng.js" type="text/javascript"></script>
<script type="text/javascript">
alert("IE6");
   EvPNG.fix('img'); 
</script>
<![endif]-->
<!--[if IE 7]>
<script type="text/javascript">
alert("IE7");
</script>
<![endif]-->
<!--[if IE 8]>
<script type="text/javascript">
alert("IE8");
</script>
<![endif]-->
<!--[if IE 9]>
<script type="text/javascript">
alert("IE9");
</script>
<![endif]-->
<!--[if IE 10]>
<script type="text/javascript">
alert("IE10");
</script>
<![endif]-->
<!--[if IE 11]>
<script type="text/javascript">
   alert("IE11");
</script>
<![endif]-->