It is there to address problems in various version of IE.
IE is not a very standards compliant browser, it has many quirks in rendering CSS that need to be accounted for in order for the menus to display in IE the same as they do in other browsers.
This portion is addressing box modal issues in IE5:
<!--[if IE 5]>
<style type="text/css">
/* IE 5 does not use the standard box model, so the column widths are overidden to render the page correctly. */
#wrapper #content #leftColumn {
width: 263px;
}
#wrapper #content #rightColumn1 {
width: 215px;
}
</style>
<![endif]-->
this porting is addressing several issues across all version of ie:
<!--[if IE]>
<style type="text/css">
/* The proprietary zoom property gives IE the hasLayout property which addresses several bugs. */
#wrapper #content, #wrapper #content #content2 {
zoom: 1;
}
</style>
<![endif]-->
this portion is addressing a problem with transparent images in ie6 and below:
<!--[if lt IE 7]>
<style type="text/css">
img, div {
behavior: url("../Website/CSSSculptor/3ColumnFixedHeaderandFooter_CaboSunset_images/iepngfix.htc");
}
</style>