Disabling Loop back Security Check

                      
                         A very common issue which you face while you work on the servers hosting Sharepoint.When you use the fully qualified domain name (FQDN) or a custom host header to browse a local Web site that is hosted on a computer that is running Microsoft Internet Information Services (IIS) 5.1 or a later version, you may receive an error message that resembles the following:

HTTP 401.1 - Unauthorized: Logon Failed

This issue occurs when the Web site uses Integrated Authentication and has a name that is mapped to the local loopback address.
Note You only receive this error message if you try to browse the Web site directly on the server. If you browse the Web site from a client computer, the Web site works as expected.
How to fix this :

1. Click Start, click Run, type regedit, and then click OK.
2. In Registry Editor, locate and then click the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
3. Right-click Lsa, point to New, and then click DWORD Value.
4. Type DisableLoopbackCheck, and then press ENTER.
5. Right-click DisableLoopbackCheck, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Quit Registry Editor, and then restart your computer.

This would resolve the issue  :-)