This article explains the managed pipeline mode option in IIS 7.
Last week when I was hosting an application on IIS7 when adding an application pool I saw the field "Managed pipeline mode". It has two values in the drop down, "Integrated" and "Classic". I became curious about the the differences between them. After application hosting I changed the value but didn't see any difference. That increased my curiosity to disover the exact differences between them. I read several blogs on this and came to understand the differences between them.
When to use Classic Mode
Sometimes legacy applications don't support the IIS 7 architecture and then the Classic mode works. When you select it, Classic mode IIS behaves like an IIS6 version.
Diving Into ASP.NET WebAPI