There's a good reason to want to use it Rated 5 out of 5 stars
Thanks to the instructions below I have Ctrl Tab Preview working in FF 3.04 just fine. Now why would I want to do this since FF 3 already has a Ctrl tab function that shows the open tabs? I found with this add-on the highlighted tab is bigger and makes it easier to select the one you actually want to go to. The built in function does not and the more tabs I had the harder it was to see which one I wanted to select. I open a lot of tabs and find this useful to navigate them in a preview mode. Still I would like to see the original developer update it for current FF versions so users don't have to manually edit the XPI file to modify the max version value. For WIndows users 7-Zip can open XPI files and from within the file you can edit the install.rdf file easily with your default editor e.g. notepad (it works).