Originally Posted by Xeratul
I'm not really sure if I understood what you want. Document windows or tabs within an application are usually switched with Ctrl-Tab. However, Firefox has been buggy concerning the tab order from early childhood, and that hasn't been fixed ever since. It does not switch between the two most recently used tabs, but instead sticks to a fixed internal tab order that doesn't correspond to the natural order (z-order) of these tabs.
Someone told me long ago there's an extension that fixes this behavior, but I forgot the name. It didn't bother me since I use Firefox so rarely, rather prefer Opera.
[X] Doc CPU