Outlook won't open in web browser

[Marianne]

When i'm on-line and I click in the IE toolbar the mail
tab which has always connected me to my Microsoft Outlook
Program, nothing happens. It seems like the settings are
still right. Internet tools is set to recognize Outlook
as my mail program. I'm running XP and when I click on
Start, All Programs, and then Microsoft Outlook outlook
opens and I can click send/receive and get my mail. Why
won't IE let me get mail through the web browser anymore?
..