Error 403: Access Denied/Forbidden

This is caused by having incorrectly specified a proxy server. To Resolve this :

1. Click on Start then Settings
2. Click on Control Panel
3. Click on Internet Options
4. Next Connections Tab
5. Click the LAN Settings button and take the tick out of use proxy server.
6. Click OK

There may also be a problem with the proxy or your trying to access a page which requires authentication

 

Check out this in-depth article from Microsoft:

http://support.microsoft.com/?scid=kb;EN-US;Q245142