You might want to google "unable to load symbols". To give you a little help,
- do a build on your project only when you want to deploy or have made significant code changes. It will take a while to build depending on your machine.
- if your project is not set to debug it could cause problems. Check this in the Solution as well as in the web.config
- clear out your .NET IIS temp files. They can be found in the following directory:
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files if you don't have a 64 bit machine, use
C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files
Also, if trying to debug your program, you're better off attaching to a process and running your site in the local IIS instance than trying to debug within visual studio's F5 ability because if you're using a website it will build the project each time (unless your settings say otherwise) and that may take a bit.