One of the changes that was in Firefox 3.6 that I didn’t like was when you open a new tab from a current page, instead of it going to the farthest right on the tab bar, it inserts it right after the current tab that is “related”. I did not like this, so to fix it;
1. type in “about:config” in the URL box
2. in the filter, type in “browser.tabs.insertRelatedAfterCurrent”
3. Double click it to go from True to False.
Much better.