"Netscape, Mozilla and also Opera have made versions with built-in support for domain names with national characters.

• Netscape 7.1 or superior
• Mozilla 1.4 or superior
• Opera 7.20 or superior
• Firefox
• Internet Explorer 7 or superior

In order to upgrade Internet Explorer 5.0, 5.5 or 6.0 to make it support domain names with national characters, you have to download a plugin called i-Nav from Verisign. Verisign have also made plugins for Outlook and Outlook Express, so that you can send and receive e-mails with national characters ."

Source: Norid.no