Just a quick notice. ".ir" TLD has been added to the IDN white-list of Firefox, and will be effective on next updates for 2.0 (Gecko 18.104.22.168) and beta-3.0 (Gecko 1.9).
Now you can use your Persian domain names, ".ایران.ir", easily in Firefox. Enjoy it!
P.S. ".ir" has been in white-list in IE since version 7.0.