To specify a port for the ASP.NET Development Server:
- In Solution Explorer, click the name of the application.
- In the Properties pane, click the down-arrow beside Use dynamic ports and select False from the dropdown list. This will enable editing of the Port number property.
- In the Properties pane, click the text box beside Port number and type in a port number.
- Click outside of the Properties pane. This saves the property settings. Each time you run a file-system Web site within Visual Web Developer, the ASP.NET Development Server will listen on the specified port.
more info: How to: Specify a Port for the ASP.NET Development Server