Use IE Tab
There is a great extension called IE tab which lets you switch rendering engines inside firefox. Its simply a right click. I like the preview, but don't use it much because I don't like my posts getting captured to the clipboard. I am a heavy clipboard user and don't like my ramblings showing up in my other programs by accident.
https://addons.mozilla.org/en-US/firefox/addon/1419
you can set some sites to always show up in an IE tab, which is what I use it for since some sites I visit daily don't support firefox at all and client's FTP sites are easier to navigate on IE than firefox.