I’m a big fan of tabbed browsing with Firefox. I pretty much open every new link in a new tab, and click most links while holding CMD – or ctrl for you PC folk – (which opens the link in a new tab while keeping the current tab in focus. However, switching or cycling through tabs was not as simple as I had hoped. Since I really like the way Adium switches through tabs (CMD + right arrow or left arrow), I found a way to recreate this shortcut with Firefox. The method is a little hairy, so if you like the way you interact with Firefox’s tabs just fine, don’t worry about applying this little customization. Otherwise, read on!
In order to do this, you install a Firefox extension called Keyconfig. Once installed, go to Tools –>Keyconfig–> Add a new key. In this window, name your new key whatever you like (I called mine Switch Tab Left and Switch Tab Right). For Switch Tab Right, replace the part that says /* Code */ with: gBrowser.mTabContainer.advanceSelectedTab(1,true); Then click OK, and in the boxto the left of the Apply button, click once and then press the shortcut on your keyboard that you want to map to switch to the tab to the right (I used CMD+right arrow). Then click apply. If you get an error about the shortcut you chose already being used, look at the list and see what action is using it, and if its not important to you, just disable it by clicking Disable. Repeat this process for Switch Tab Left, this time replacing /* Code */ with gBrowser.mTabContainer.advanceSelectedTab(-1,true); and mapping the shortcut to the combination that you want for switching to the tab to the left (I used CMD+left arrow).
Keyconfig is a great little tool that adds just that little bit of flexibility. Check it out if you’re interested in changing some things about Firefox.