This is one of these things that bother you but not enough to make you take any action about them.

Ever since I started using Visual Studio I've been bother by the fact that if your solution contains multiple web projects, when debugging, an instance of "ASP.NET Development Server" is started for every one of them, even if you have selected a "Single startup project" on your Solution properties.

Finally I decided to investigate how to launch only the project selected. This is how:

1. Select one of the web projects and press F4 to open the Properties window.
2. Under "Development Server", set "Always Start When Debugging" to "False".
3. Repeat for all other web projects in your solution.