ASPX not redering CSS images

I am trying to use the same code that works fine as stand-alone HTML into an ASPX page in .NET.
Everything works just fine (scripts, layout, paths, etc), except it appears that the images from the CSS file are not being rendered. I know it’s finding the CSS, but I don’t know why it’s not grabbing the images.

Anyone have any idea why this would happen?

Code:

AJAX Application <%----%>
 <style type="text/css">
     html, body {
    	width: 100%;
	    height: 100%;
	    overflow: hidden;
	    margin: 0px;
	    background-color: #EBEBEB;
     }
  </style>
var myLayout, myTree, myGrid, myFolders, myMenu, myToolbar; ...

OK, I got it to work!
I ran the default dhtmlx.css through a validator at w3.org.
It didn’t like 259 things. What it did like, I pasted back into the CSS and it worked.
So I guess IIS is more picky about the validation that my browser???

We will investigate the issue, while css contains some elements which are not-standard ( rules for old versions of IE ) there is no direct errors, which must cause such result.