Keyboard shortcut for switching between tabs in Firefox 2

It's Ctrl + TAB to switch tabs in Firefox

here you go:

 click Ctrl+Page Up to move to the previous tab, or Ctrl + Page Down the the next. You can also try Ctrl + # (a number, on the upper numbers line) to a select a specific tab.

I also recommend using "Tab Catalog" add on - really makes life easier. 

helinus' answer is correct, I don't understand why someone gave this answer a thumb down. What I like about ctrl-tab is that it works in other apps as well, for example if you have a few open documents in Word you can switch between them with ctrl-tab.

Raanan's answer is also good. I recommend the Tab Mix Plus extension, while we're at it. 

The keyboard shortcut is "Ctrl + Tab" to switch between  tabs.

ctrl + pgup or pgdn

hotkey: Firefox keyboard shortcut to switch between tabs (Linux)

On Linux with the KDE desktop, ctrl + tab switches between KDE virtual desktops, so it doesn't switch tabs in Firefox. "ctrl + page up" and "ctrl + page down" cycles through tabs, and "alt + <tab number>" works from left to right. So tab number 1 is the left-most tab, tab 2 is the next tab, etc, up to "tab 8". Example: Press "alt + 3" to switch to the third tab. "tab 9" will take you to the last tab - regardless of what number the tab actually is.

hotkey: Firefox keyboard shortcut to switch between tabs (Linux)

On Linux with the KDE desktop, ctrl + tab switches between KDE virtual desktops, so it doesn't switch tabs in Firefox. "ctrl + page up" and "ctrl + page down" cycles through tabs, and "alt + <tab number>" works from left to right. So tab number 1 is the left-most tab, tab 2 is the next tab, etc, up to "tab 8". Example: Press "alt + 3" to switch to the third tab. "tab 9" will take you to the last tab - regardless of what number the tab actually is.

Nikon D90 : Simple operation - TAB with Ctrl