From time to time you need to define a fixed port for web projects during development, an example may be a need to exercise services through a proxy for testing.  This can be fixed in the SLN file to ensure that for all solution users the port is fixed.

Find the project in the SLN, and VWDPort setting will be defined, set the required port and add VWDDynamicPort = "false" setting below.  once reloaded the solution will always use the chosen port.