Add-ons developers need to test their add-ons with new versions of Firefox before marking them compatible. Until then, you can use the Compatibility Reporter add-on to try out untested add-ons, and report whether they work:

https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/

Some users have reported that Selenium IDE does work in Firefox 4 when the Compatibility Reporter is installed.

Worked great for me.

Instaled compatibility reporter and now runs perfect.

Many thanks mbrubeck.

I was able to see selenium IDE after installing this plug. But simple record and play did not work. (eg google anything - click on a link and play it back)

Bear in mind you need two things two make selenium working in FF4.0.1

1. compatibility reporter add on
2. selenium 1.0.10 (http://release.seleniumhq.org/selenium-ide/1.0.10/selenium-ide-1.0.10.xpi)

Thanks for this!

When I open Selenium IDE, it only shows me the "Source" tab, but not the Table tab. Is there a way that I can enable the Table tab? Thanks for your help.