In Ubuntu 8.10 after installing Firefox 3, I received an e-mail that contained a mix of Arabic and English words and since the default text direction is left-to-right, it was very difficult to read and I couldn’t find the context menu option “Switch Page Direction”! I then did some googling and I found out how:

1) in the URL, type “about:config”
2) In the “Filter:” text box, type “bidi.browser.ui”
3) The “bidi.browser.ui” entry was set to “false” in the “value” column. Change it to “True”
4) Restart Firefox
5) Right-click and you’ll find it there 🙂
6) Enjoy!