Internet Explorer version 8 has got some annoying loopbackcheck. Whenever you want to browse a local hosted site (IIS), it will pop up a security dialog in which you have to fill in your username and password.
Whatever combination you fill in, eventually you will get a 401.1. error.
You can resolve it by editing the the registry.
- Click Start, click Run, type regedit, and then click OK.
- In Registry Editor, locate and then click the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
- Right-click Lsa, point to New, and then click DWORD Value.
- Type DisableLoopbackCheck, and then press ENTER.
- Right-click DisableLoopbackCheck, and then click Modify.
- In the Value data box, type 1, and then click OK.
- Quit Registry Editor, and then restart your computer.








