New tabs do not appear to the right of the last tab

In Firefox 3.6, new tabs created from opening links are positioned next to the current tab. This behavior makes it easier than before to keep similar tabs close together.
If you would like to use the old behavior from Firefox 3.5 and earlier, in which new tabs open at the end of the tab strip, you can set configure this through the advanced configuration.

1. In the Location bar, type about:config and press EnterReturn.
   • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page.
2. Search for the preference browser.tabs.insertRelatedAfterCurrent.
3. Double-click on browser.tabs.insertRelatedAfterCurrent, which should set the value to false.

If you ever want to change it back, repeat the steps above, which will toggle the value back to true.
For more information about tabbed browsing, see Tabbed browsing.