If you want to use the Mac OSX built in jabber client "ichat" and you want to use jabber80.com to avoid the firewall or proxy, then you should follow these instructions:
From the main menu, choose iChat->Preferences
In the Accounts tab, choose add a new account (+):
From the Account Type, choose "Jabber Account":
Now fill the data with your jabber80.com account. Remember that you have to use your own data. The data shown on the image are my personal data:
Now choose "Server Settings" and fill in as shown: Server has to be jabber80.com; port 80; Uncheck using SSL
You now have a fully functional jabber80.com account. Please note that the MSN gateway is active and one contact of mine was online at the time of taking the screen-shot. No one ICQ contact was online, so none is shown.
As usual, any doubts or questions, please mail me: mlvp30_at_jabber80.com