Firefox for Web Developer?

Is there any FireFox plugin which acts the same as IE8 developer tools in a way that it has an option to switch from different modes or versions?

I had many issues when installing different versions of FireFox in just one machine. I now have 3.0, 3.6, 4.0.开发者_如何转开发1 and 5.0.1 of FF but I got a problem regarding add-ons, it seems like they share just one location where add-ons are in.

If I open FF 3.0, since some add-ons are latest version for 4.0.1 and are not compatible with FF 3.0, it will disable them, then when I go back to the later version, add-ons which was disabled by the older FF will be gone.

Anyway my platform is Windows 7 32-bit.

Start firefox with following option

• firefox.exe -ProfileManager

For each profile you can add individual addon's which do not conflict with other profile addons. Ensure you give different names for different profiles in different firefox versions.