Consider this web page fragment:

    <!--[if gte vml 1]> <v:imagedata src="image1.gif"/>
<![endif]-->
    <![if !vml]><img src="image2.gif" <![endif]>

IE6 (with vml) renders image1 on the target website.
HTTrack only downloads image2, and then IE6 tries to 
render image1 in the mirror, which fails.
Netscape (no vml) renders the mirror with image2 correctly.

Is there any way to get HTTrack to download image1 in spite 
of the comment?