A change in the default behavior is often problematic for many users. Firefox 3.6 has introduced a change in the way new tabs are opened. Before Firefox 3.6 tabs were always opened at the right in the web browser which meant that tabs were added as a new tab at the end of the tabbar in the Internet browser.
In Firefox 3.6 however only new tabs are opened at the far right of the tabbar while new tabs that are opened from existing tabs, e.g. by middle-clicking a link in an already open tab, are opened next to the tab containing the link.
That feels like inconsistent behavior to some Firefox users. Those who prefer the old way of opening new tabs (all at the right end) can make Firefox 3.6 change that behavior to the default behavior of previous Firefox versions.
The changes are made in the about:config configuration window. Simply enter about:config in the Firefox address bar to open the configuration menu. You might need to get past a warning message if that is the first time you open that menu.

Now filter for the term tabs.insertRelatedAfterCurrent. The default value of the parameter is true which simply means that related tabs are opened after the current and not at the end. A double-click on the row will change the value to false indicating that related tabs will from then on be opened at the end of the tabbar just like new tabs.
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Thanks!
This was starting to get on my nerves.
For me the same like mindmaze wrought and i am really missing main tab mix plus add on. Do you know any add on like tab mix plus which is working with Mozilla Firefox 3.6?
Cannot you force compatibility?
i have tried it with the (new) add-on Tab Utilities 0.5 and i have also tried it follow the lead from the how to geek with his new checkCompatibility trick way (Make Your Extensions Work with Firefox 3.6) but now dice. After forcing the tab mix plus add on the add on does not work correctly.
Thank you! Thank you! Thank you!
try the combo of verttabbar, faviconizetab, and tabmixplus
awesome setup, especially for small notebooks, macbooks, netbooks
Thanks! I thought I was going crazy!
Don’t know how recently this updated, but TMP is now 3.6 compatible. And does this by default.
Any add-on for FF 3.5 to open a new tab next to the tab containing the link ?
(like in FF 3.6)
tab mix plus has that option and many more. awesome extension
thank you wish developers would stop changing things everyone is used to for many years. wish would spend time making faster, faster, faster instead of feature feature feature
Yay!! thanks!! I hated that
Finally I can get rid of Tab Mix Plus which causes so much troubles on Firefox CPU usage. I actually prefer the other way and found that Ubuntu disables that!