Conclusion: After the administrator password of the SharePoint Management Center is modified, access to the newly created site is denied.

Background:

The domain user acts as the administrator of the management center, and the domain user needs to change the password on a regular basis. When a new application is created, the Access Denied problem occurs.

After changing domain user password, it is denied to access new application.

 

Solution:

Add:Disableloopbackcheck

 

Procedure:

 

 

Ive found this very handy .. recently, I was working on a server and we were trying to access the local SharePoint site http: // 127.0.0.1 or http: // nameoflocalserver/pages/default. aspx and I was constantly prompted for the username and password. in SharePoint 2010, it can really annoy you by not accepting your Username Password credentials in the popup window.

Its a 'feature 'on the server that you need to disable as a workaround.
Caution: Microsoft best practices is out of scope in this article. Do your own research on this topic.

You wowould need to create a DWORD registry key in the registry calledDisableloopbackcheckAnd set it to 1.
Follow these steps:

Option 1: Add this registry entry by powershell

 
New-itemproperty HKLM: \ System \ CurrentControlSet \ Control \ LSA-name "disableloopbackcheck"-value "1"-propertytype DWORD
 

Option 2: add this registry entry manually

Click Start, click Run, TypeRegedit, And then click OK
In Registry Editor, locate the following registry key:HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ LSA
Right-click LSA, point to new, and then clickDWORDValue. (In win 2008, itsDWORD32bit)
TypeDisableloopbackcheck, And then press Enter.
Right-click disableloopbackcheck, and then clickModify.
In the value data box, type1And then click OK.
Quit Registry Editor.
You may needRestartYour server.

For more information about this, click the following article number to view the article in the Microsoft Knowledge Base: 281308 (http://support.microsoft.com/kb/281308) connecting to SMB share on a Windows 2000-based computer or a Windows Server 2003-based computer may not work with an alias name.

 

 

Source: http://www.jeremytaylor.net/2010/05/24/sharepoint-disable-loopback-check-disableloopbackcheck-dword-in-registry/