Why we use 'Static' in class declaration statement

From MSDN:

A class can be declared static, indicating that it contains only static members. It is not possible to create instances of a static class using the new keyword. Static classes are loaded automatically by the .NET Framework common language runtime (CLR) when the program or namespace containing the class is loaded.

http://msdn2.microsoft.com/en-us/library/79b3xss3.aspx

I hope this helps.