I am using Firefox 8 as my homepage and my att.net Mail Preview will not load.

My internet service provider (IPO) is AT&T, but I use Mozilla Firefox for my home page. A facility on my home page that permits me to check my e-mail has ceased to load. The tab that normally permits me to do that is "att.net Mail Preview". The tab is still there, but below that tab appears "loading . . . . .". But, it never stops loading. I don't actually use this subject e-mail facility to send and read e-mails, but I do use it to determine what e-mails are available. When the facility is working properly it has the capacity for me to send and receive e-mails, but I chose to not use.