Cannot Run Web Application

Problem: ASP.NET web application can not be run.
Error: WebDev.WebServer.exe has encountered a user-defined breakpoint.

Solution:
The web application you are developing is using Visual Studio development server with dynamic ports. At the same time, you have the same or another web created and running under the same port in IIS.
1. Either stop the IIS for the web which is using the same port as the web application you are going to run under visual studio development server.
2. Or, change the port number of the web application running under visual studio development server. To do this, click on the website, then change the port number in the Properties Window.