Had no problem with Firefox 3.6.15 and now Firefox 4.0 with the WebRep icons in Google search results. I don’t use Yahoo search but just tried it and the WebRep icons are missing in Yahoo search.
This on WinXP Pro SP3 with Avast Free 6.0.1035 Beta.
Edit: Just realized that Yahoo search results page requires JavaScript enabled for the page to see the WebRep icon on the urls, while Google search doesn’t.
However, both results pages require JavaScript enabled for the WebRep pop-up on hover.