SharePoint prompts user for credentials (login/password)

In MOSS - I found this could be due to following reasons:

1. If you are not using proper authentication in IIS for web app, in this use integrated authentication.
2. It may due to proxy settings(if you are using a proxy server (intranet)) , in this case go to tools in IE--> internet options --> connection--.LAN settings --> advanced --.> exception. Add the site over there.
3. If you have sync setup with mysite or lists with your outlook, in this remove it from your Outlook profile.
4. due to IE unable to authenticate user when using IE 7 and 8 with SP 2007.  To fix that follow these steps.

• Go to Internet Options -> Security tab
• Select Trusted sites Zone -> Click on Sites ->Add the SP site to Trusted Sites. (http://*.yourdomain)
• Then check the settings under Custom Level (for trusted sites) - scroll to the bottom and look at the Security settings for User Authentication. Make sure it's set to Auto Logon with current user name and password.
• Click OK and OK again. Restart IE and try your site.

If SharePoint prompt when opening Office documents, try this registry change:

1. Click Start, type regedit in the Start Search box, and then press ENTER.
2. Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters
3. On the Edit menu, point to New, and then click Multi-String Value.
4. Type AuthForwardServerList, and then press ENTER.
5. On the Edit menu, click Modify.
6. In the Value data box, type in the following:
7. http://*.your domain
8. Exit Registry Editor