Do you like to use Firefox, but occasionally you need to visit sites that require Internet Explorer, e.g. they have ActiveX controls? Or perhaps you need to test web pages in multiple browsers? Then you should try IE Tab!!! This Mozilla add-on uses the Internet Explorer rendering engine within Firefox so you don’t have to open a new browser. If you’re at a site and want to switch to IE, just right-click on the tab and select Switch rendering engine to re-load the page. If there are sites that you always want to open in IE, then add them to the IE Tab sites filter from the Tools… IE Tab Options dialog box.

IE Tab Options

I find this to be a very useful plugin.