You may be working in a ''dialog window''. Starting in Firefox 4, it is intended behavior that a dialog window not be able to have new tabs. However, the developers may have applied this principle to too many styles of windows merely because the window is "small." To open a new "normal" window, you can press Ctrl+n or use File > New Window. --- A bug already has been filed (many, actually) complaining about this change, and suggesting some tweaks to this feature so that it only affects popups which were truly intended to behave like dialogs. Current functionality: [https://bugzilla.mozilla.org/show_bug.cgi?id=606678 Bug 606678 "Open Link in New Tab" shouldn't add tabs to popups] Requested change: [https://bugzilla.mozilla.org/show_bug.cgi?id=644729 Bug 644729 – Popup window with all toolbars visible causes new tabs to open in another browser window] Because posts on a bug get sent to everyone on a long mailing list, it is considered poor etiquette (spamming) to add "me too" comments to a bug. However, you can "vote" for a bug to get fixed, so it might be worth registering on Bugzilla to do that if you are affected by this on a day-to-day basis. --- As a temporary workaround, I created a Greasemonkey userscript. It adds a button to pages detected to be in a dialog window so you can reload them in a regular window. As a 0.1 version it's not perfect, but if you run into this problem frequently, hopefully it will help. [http://userscripts.org/scripts/show/101728 Dialog To Normal Window on userscripts.org] (requires the Greasemonkey add-on)