Firefox 3.6 has been released for some time, because individual extensions are not compatible with the latest version, so it has not been upgraded, including Web Developer's essential IE tab and not compatible with Firefox 3.6.
Here recommend a best IE tab replacement plug-in- Coral IE tab.
Coral IE tab, is a branch from the IE tab extension, it inherits the IE tab in Firefox call IE's kernel function, so not only for Web developers to debug Web pages in different browsers compatibility more convenient, and for the general use Users, when you encounter Firefox can not normally browse the Web page, you can easily switch to IE to display.
It has two major improvements compared to the Ietab:
1. Support Adblock Plus, so you can filter ads with Adblock Plus in the IE engine.
2. Support cookies so that when you switch between Firefox and IE, you don't have to log in again.
Coral IE tab in my opinion, the only bad thing is that the right button operation option uses the level two menu mode, for users who are accustomed to IE tab, to a large extent, increased operating costs.