A project with an output type of class Library cannot be started directly in asp.net

This error is caused in asp.net when you are working in n-tier architecture in asp.net and try to run the solution in the browser. Error Sanpshot is given below:

How to Solve Error project with an output type of class Library cannot be started directly in asp.net:

To solve this error Right click on the Presentation Layer of project in Solution Explorer and Select the option Set as Startup Project.