这段代码用来判断ie的版本,不同的版本调用不同的样式
<!-- [if IE]>--> According to the conditional comment this is Internet Explorer <!-- [if IE 5]>--> According to the conditional comment this is Internet Explorer 5 <!-- [if IE 5.0]>--> According to the conditional comment this is Internet Explorer 5.0 <!-- [if IE 5.5]>--> According to the conditional comment this is Internet Explorer 5.5 <!-- [if IE 6]>--> According to the conditional comment this is Internet Explorer 6 <!-- [if IE 7]>--> According to the conditional comment this is Internet Explorer 7 <!-- [if gte IE 5]>--> According to the conditional comment this is Internet Explorer 5 and up <!-- [if lt IE 6]>--> According to the conditional comment this is Internet Explorer lower than 6 <!-- [if lte IE 5.5]>--> According to the conditional comment this is Internet Explorer lower or equal to 5.5 <!-- [if gt IE 6]>--> According to the conditional comment this is Internet Explorer greater than 6