А слабо было использовать разные css файлы и подключать их через Conditional comments:

Код:
<!--[if IE]>
According to the conditional comment this is Internet Explorer

<![endif]-->
<!--[if IE 5]>
According to the conditional comment this is Internet Explorer 5

<![endif]-->
<!--[if IE 5.0]>
According to the conditional comment this is Internet Explorer 5.0

<![endif]-->
<!--[if IE 5.5]>
According to the conditional comment this is Internet Explorer 5.5

<![endif]-->
<!--[if IE 6]>
According to the conditional comment this is Internet Explorer 6

<![endif]-->
<!--[if gte IE 5]>
According to the conditional comment this is Internet Explorer 5 and up

<![endif]-->
<!--[if lt IE 6]>
According to the conditional comment this is Internet Explorer lower than 6

<![endif]-->
<!--[if lte IE 5.5]>
According to the conditional comment this is Internet Explorer lower or equal to 5.5

<![endif]-->
в вашем xhtml файле?