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This code (currently 2.0b3) by Dean Edwards is a js library to make MSIE behave more standards compliant. The theme code is only recognized by IE and is for the version 5.5 and 6 browsers as they have a number of problems dealing with PNG image files (they had problems with the alpha layers) as well as the W3C box model, among other things. While
there are still users using IE6, it continues to fall, and it's a horrid browser from a standards compatibility standpoint, thus
the campaign to rid the world of IE6.
That aside, you may be able to use a later version of this script. More information is at
the GoogleCode site for IE7 (now updated for IE8 as well).
Are you using other java script libraries or frameworks like jquery? Do you have the same problem in IE as you have in Firefox (I'm assuming you are using IE)? When you say the color, styles on page edit, are you using a WYSIWYG editor and if so which one? Weird that it stops most of your scripts. I'll have to see how it works on my sites. I've used the PNG fix version, but nothing like this related to the box model.
I also saw that you can defer the scripts loading time by adding the 'defer' attribute to your other script loads and see if that helps:
<script defer type=...>
If your scripts use className to change the look (a high liklihood), then you may need to look at
the caveats page.
Good luck!