User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:2.0b12pre) Gecko/20110208 Firefox/4.0b12pre Build Identifier: Mozilla/5.0 (Windows NT 5.1; rv:2.0b12pre) Gecko/20110208 Firefox/4.0b12pre If there is a submenu within a menu which is too long to fit on the screen (ie has the scroll arrows on top and bottom), then once scrolled the submenu positioning fails to update, as illustrated in this image (the top half shows it unscrolled, the bottom half is when it has been scrolled down and shows how the submenu fails to update its position): http://ompldr.org/vN2NjdA/fxbug.png Additionally if the mouse is moved to the place illustrated in the image, Firefox highlights "open all in tabs" as if the reposition had taken place, which is an obvious visual glitch. Reproducible: Always Steps to Reproduce: 1. On the bookmarks menu create a test root folder. 2. In the test folder create as many dummy bookmarks as is necessary for it to overflow. 3. Create a child folder in the test folder, in the midst of the dummy bookmarks. 4. Mouseover the folder when scrolled to the top. Note that the submenu appears in the expected location. 5. Dismiss the submenu and scroll down a bit. 6. Mouseover the folder. Note that the submenu has not moved. 7. Try to select some child items in the submenu. note that it "thinks" it has moved. Actual Results: glitchy (lack of) positioning, frustrated user Expected Results: reposition with scroll, happy user I am not sure whether this only affects the bookmarks toolbar or all of firefox's menus. Also note my unusual layout. This may have an effect - I have not tested it with other layouts.