OWA segmentation provides the ability to selectively enable features of OWA. For example, you can disable or enable mail, Calendaring, Contacts, public folders, Calendar reminders, new mail notification, and MS IE 5 support according to service offering. Administrators can segment OWA into different support offerings in Exchange 2000 Server Service Pack 2 (SP2) and later. You can segment OWA on a per-server or a per-user basis. Per-user settings override per-server settings, if both are in place.
http://support.microsoft.com/?id=311154
A Few Important Troubleshooting Tips
1, When you are finished with your mail you must click the Log Off icon AND go to the FILE menu and choose either Quit or Close. If you don’t do both steps, you leave your e-mail account open to the next web browser user!
2, If OWA appears to freeze while you are using it, click on the Refresh or Reload icon on the top of the browser window. This should get things going again. If that doesn’t work, press Control N on your keyboard and a new page should appear. If you have tried the first two options and the computer is still frozen, click the browser window Close button.