CLS is stand for ( Common Language Specification ) and it is set of languages features which supported by the Common Language Runtime (CLR) of the .NET Framework. CLS is also part of the .NET Framework which is help in runtime environments. It is designed to support language need which is commonly used by developers and to produce verifiable code. These variables codes are allows all CLS compliant languages to ensure the type safety of code. CLS common to many object oriented programming languages. CLS main function is provides the guidelines to the compiler of a language which do task on the .NET Framework. CLS compliant code is the code exposed and expressed in CLS form. In .NET framework CLS play an important role to designing web applications.