I\'m new to ASP.NET-ville, be gentle.
I have been troubleshooting a ASP.NET setup, where the server/database values are changing, therefore web.config needs to be up
There are two different types of connection strings here. The best bet (IMO) is to have a read up in the docs -
The first is an ADO.Net connection string: http://msdn.microsoft.com/en-us/library/ms254500.aspx
The second is an Entity Framework connection string: http://msdn.microsoft.com/en-us/library/cc716756.aspx
It's all explained in those two links, certainly clearer than I can explain it!