IE Tab allows users to view pages using the
Internet Explorer rendering engine from within Firefox. This may be useful for viewing pages that only work in Internet Explorer (e.g.
Windows Update) without exiting Firefox. Pages viewed through the IE Tab extension will be recorded in Internet Explorer's history,
cache, and so on, as if they had been viewed directly in Internet Explorer. The extension has become popular among
web developers, since they can display and compare their websites in the two browsers simultaneously.
Download and try it from here. (
https://addons.mozilla.org/en-US/firefox/addon/1419)
Screenshots :


Reference :
http://ietab.mozdev.org/