On Mac, the keys to switch to next/prev tab are different in different browsers. They are:
And in Opera it's the 1 and 2 on numberpad. Opera has always been the funky one, but i must say here it's the most efficient choice here 〔☛ Opera Pain〕
They are different on Windows too. The choices there are typically 【Ctrl+Tab ↹】 or 【Ctrl+⇟ Page ▽】.
F��� it. F��� them.
Best solution: get a Microsoft Keyboard and use Microsoft IntelliType, so you can create one hotkey that works across apps. This solution is simple, easy. No diddling with config files or scripting. Works pretty much the same in both Windows and Mac. (except Linux, too bad for penguins). Plus, you get a keyboard. (See: What Microsoft IntelliType Review) Possibly Logitech keyboard will also do. Other than that, you have to resort to each OS's tools. See: Keyboard Layout ＆ Key Macro tools for Windows ◇ Mac OS X Keyboard Layout, Keymapping, Keybinding, Tools.