Unable to start program 'http://localhost/Default.aspx'. VS2010

Question

I cannot start my website from Visual Studio 2010 anymore.

For a few days I cannot start my project in a web browser using F5. When I open my web application directly by

Answer 1

I had this exact problem with Visual Studio 2008. The solution was to set the default web browser that VS uses to a real browser (e.g. IE) and not the "Internal Web Browser".

1. Right click on an ASPX file in your project and select "Browser With...". This lets you select the default browser to use when you select the "View in Browser" option and for when you debug/run the app (this is key).
2. Select your favourite browser (i.e "Internet Explorer") and click on "Set as Default". Do not pick "Internal Web Browser".
3. Debug away! Your app should come up in your browser now and debug as normal.

Answer 2

Try to turn on Bypass proxy for local addresses. First you can go to your browser settings-> Change proxy Settings-> Connection-> Lan Setting and just check bypass proxy for local addresses. If this solution don't work then also copy the following code check your web.config file for settings to bypass firewall:

<system.net> 
 <defaultProxy> 
  <proxy usesystemdefault="true" proxyaddress="http://proxy:port" bypassonlocal="false" /> 
 </defaultProxy> 
</system.net>

Answer 3

For me I just did a Build /ReBuild on the project level and it started working!!!