Vista and Firefox “bouncing screen”
Recently Vista updated itself, and after this certain web sites would “bounce” when viewed in Firefox. The bookmarks also disappeared - not the ones under the “Bookmarks” menu, but the ones between the navigation bar and the browser content. Bit frustrating, and led to using IE for a while before finding the time to investigate. Anyway, it’s easily solved by right-clicking on the grey area between web page content and navigation bar, and adding a new bookmark.
Thanks to http://kb.mozillazine.org/Window_shakes for the solution 