ASP.NET is a rapid-development language which allows you to offer value-for-money solutions with tight deadlines. Writing Web applications with ASP.NET is easy. However, you may find the application is not running as quick as expected in a realistic environment and will need performance-tuning.
This WHY Map is not intended as the definitive guide for performance-tuning ASP.NET Web applications. As Rob Howard mentioned in his MSDN article, an entire book could easily be devoted to that. However, the areas covered here are good places to start based on my own personal experience..