User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:2.0b8pre) Gecko/20101009 Firefox/4.0b8pre Build Identifier: Mozilla/5.0 (Windows NT 6.1; rv:2.0b8pre) Gecko/20101009 Firefox/4.0b8pre The windows moves without user's control. the only reason for this is only one tab. Reproducible: Always Steps to Reproduce: 1. Go to www.nobrain.dk (NSFW) 2. 3. Actual Results: Now Firefox window moves to right and left, and back to right and back to left and so on... It is not possible to catch up the close button of the window and the other close buttons. Expected Results: Window should not move. The user should be able to close the other tabs without problem. If the user is at work and somehow he or she clicks the button then it is possible for him or her to be fired. Thus, "the moving of window" function should be removed.

Edit Preferences... under "Content" tab, click "Advanced..." next to the "Enable JavaScript", uncheck "Move or resize existing windows"

I don't think that every Firefox user will be aware of the page here when he or she falls in trap. Most Firefox users are not aware that this option exists. Even if they know they will not uncheck the option before they enter the site.

I think that move part should be unchecked by default as it is in Opera and Chrome. I don't know whether there is an option or not in Opera and Chrome but they do not move the window.

Ok, so you morphed the bug into a request that we change the default. This is a known problem (since many years) so filing new bugs doesn't help. See the dependent bugs on bug 432687. Bug 186708 and bug 502561 deals with this problem already.