unable to launch iis express web server port 80 is in use

http://blog.lextudio.com/2012/10/port-already-in-use-then-who-uses-it/

If you already have something monitoring port 80 (such as full IIS), then you cannot use another thing to monitor the same port.

Thus, if you do want to use IIS Express, make sure in Project Url: field you specify another port number other than 80.

In VS 2013:

Go to your Web Project Properties, Web Tab.

Select "IIS Express" from the dropdown.

Enter a project URL, such as http://localhost:64510/

If you have "Override application root URL" checked, uncheck it.

The port is probably in use. I usually end the iisexpress.exe. This works if for some reason the port is open and you want to close it.

CTRL+ALT+DEL -> Task Manager ->End process for iisexpress.exe

I just had this happen to me, and didn't understand why as everything had worked fine until restarting my machine. Seems that the full IIS service was running, but only within the manager had it been STOPPED, so when I restarted it turned back on.

FIX IT THIS WAY:
Open up the Internet Information Services (IIS) Manager (use search programs and files, too. See image)

Right click on localhost (top level, left pane), select STOP. Not called 'localhost'? This will probably be called your machine name, but if you hover over the top level on the left pane, you should see 'https://localhost/'. This is what you want. Right click and select STOP.

Now, this is assuming you only want to run IIS Express sites, as anything that required the full IIS won't be running. You should be good to go!