Yep I get the same thing on my Mac Book Pro and my G5. The & t comes on full forum view. I thought maybe this had to do something with the upcoming beta project. I still use the Safari 2.04.
I see the "&t" too, using Safari 2.0.4. The Safari window does not need to be stretched, and does not disappear if the window is made very narrow. I only see the &t when viewing a list of topics within a forum (eg. "Apple News, Rumors & Discussion," "HOWTO & FAQs," "iPhone," etc.), I don't see it when at the top level of the forums (http://macosx.com/forums/) or when viewing a particular thread. I had a look into the page source and found the &t appears at the very beginning, just before the document type declaration.
Okay. See it now, too, in the forum overview pages. The error is in the code, it seems. Before the doctype, there's "&t"... (oh, you've mentioned that already as well, bbloke...) ScottW?