http://www.firefoxfacts.com/2010/01/22/firefox-3-6-fix-open-new-tabs-in-far-right/
Make New Tab Pages Open in the Far Right of the Tab Bar
- Type about:config in the address bar. Then, if needed click the “I’ll be careful, I promise!” button.
- Next, in the filter box – type in:
- tabs.insertRelatedAfterCurrent
- Right-click that about:config entry, and select “Toggle”
This will convert Firefox back to loading opening a new tab from a web page on the far right of the tab bar, rather than right next to the tab you opened it from.
To switch back, follow these same steps and toggle the “false” back to “true”.
This should help those of you out there who do not like this new feature to Firefox 3.6, or are just not ready to switch how you open a page in a new tab just yet.