I’ve upgraded my system to Windows 7 couple of months ago, but I haven’t used web development.

The Problem
Few days ago, I created empty web application, added new page and added <p>bla-bla<p>, then I hit Ctrl+F5 and my default browser opened, but nothing happened. I was thinking that it is because of my browser, so I switched over 3 browsers and nothing helped, I also thought that it VS2010 broke something causing asp.net development server issues, so uninstalled it and installed back, but nothing helped.

I even had a thought to reinstall system, but decided to search over the internet more deeper and found that:

Reason
Reason is that when system uses IPv6 browsers could have issues with resolving localhost. 

Solution
Disabling IPv6 is solution for this problem.

You can disable IP 6 in your system by ensuring that you have this in your registry:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpip6ParametersDisabledComponents set to 0xffffffff

Firefox settings change
Also when searching I found for myself that we can change settings of Firefox with writing about:config in address bar.