User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; ru; rv:1.9) Gecko/2008052906 Firefox/3.0 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 6.0; ru; rv:1.9) Gecko/2008052906 Firefox/3.0 After opening about 10 tabs, on tab bar no space left for double clicking. So I can't create new tabs by double clicking on right part of tab bar. Reproducible: Always Steps to Reproduce: 1. Open about 10 tabs 2. Try to create a new tab by double clicking on tab bar Actual Results: No way to create a new tab by double clicking Expected Results: A new tab is created.

Firefox does not leave any space by default after a certain amount of tabs have been opened. If necessary, you can right click anywhere on the tab bar (even over top of existing tabs) and select "New Tab" from the menu. You can also customize the main toolbar to include a "New Tab" button for one click access to new tabs.

Does the above methods in comment 1 solved your problem or please test with the latest firefox.

This was basically fixed by bug 455756.