If you are trying to debug ASP.NET applications on Vista you might run into the following problem:

localhost is not accessible through your browser and the error that is displayed is "Internet Explorer cannot display the webpage".

After some googling I ran across a reference to the same problem.

The problem has to do with the fact that there are 2 entries for local host in the hosts file ([Windows directory]\System32\drivers\etc\hosts).

One for ipv4 and one for ipv6.

Example:

127.0.0.1 localhost
::1 localhost

To solve the problem you can remark one of them. The example below remarks the ipv6 entry.

127.0.0.1 localhost
# Causes problems when using localhost ->
#::1 localhost

Note that you might not be able to modify the hosts file even if you are running as an administrator.

The following Microsoft KB explains how to change the hosts file:

http://support.microsoft.com/default.aspx?scid=kb;en-us;923947

Hope this helps...