I have this strange problem when browsing Google Groups. The sidebar, the one displaying the various menu options, like Home, Discussions, Pages, is rendered on the left side of the page on top of the group discussions space.
Below is a snapshot taken from FireFox (version 3.5.2). I have experienced the same problems with other browsers several times as well, but FireFox is my main browser and it is really broken there.
Based on the screenshot you provided and the content of the ads, my guess would be that the problem is within the RTL-detection logic of either Firefox or the Google Groups page. If you have specified Hebrew at the top of the accepted languages in Firefox, that's most probably the culprit. You can try putting English at the top to see if that fixes the problem.
Disclaimer: I don't use Firefox at all, so the above is based purely on my observation of the behavior of other browsers and general globalization/localization knowledge. YMMV. :-)
