Online presence information doesn't appear

• Does your account have an e-mail address specified?  The presence information appears only when the e-mail address for a person is specified. A user with a blank e-mail address that has only the DOMAIN and username specified will not appear as online.
• Do you have a Windows SharePoint Services-compatible client installed?  You must have a compatible client such as Microsoft Office 2003 to view presence information.
• Is the virtual server for the site configured to display online presence information?  By default, this feature is turned on. However, an administrator may have turned this feature off.