In Firefox 3.6, when you "open link in new tab" (ctrl+click) the "related" tab opens to the immediate right of the current tab, instead of the end of the line as it did in 3.5. Personally, I like this change. If you want to revert to the old way, follow these steps.

Type the following in the AwesomeBar:

You will recieve a warning telling you that this may void your warranty.
click the button that says "I'll be careful, I promise!"

Type the following in the Filter bar:

Double click the line showing. The value will change to false & the text will turn bold to show that it is not the default setting.