Sql Server user login for a Web Application

I'm want to create a SQl Server login for a IIS web application. Since the Web Appl开发者_StackOverflow中文版ication using IIS 7.5 identity, and in addition in production the Sql Server may be in a separate machine, I'm looking for use a user and password based connection string.

Now, I'm a little confused how to create this login in Sql Server 2008 R2. Should I use databawse specific User, or a global login? Should I Database Role or Application Role?

What are the best practices to get a login for an IIS application that don't use Stored Procedures, but makes a use of an ORM tool, like NHibernate?

The following article:

http://msdn.microsoft.com/en-us/library/bb882673.aspx

recommends using Integrated Security to connect to the database.