Opera and IE Fixed (Sorta)
Okay, it seems the deal with the page being invisible in IE and Opera was due to the script tag—they were insiting on a close tag for the script tag, rather than the XML-style abbreviated form. I assume this is due to the mime type the pages are being served under; it is XHTML otherwise. Oddly, none of the web-based HTML/XHTML validators complain about this. Anyway, thanks to Zoran Lazarevic for helping me figure this out.
I guess that explains why 72% of my hits are from Mozilla variants.
Now I just need to make the comment-field-collapsing script work in IE. (Does it work in Opera?)