While working with ASP.NET, it is a very common issue with the ClientID of each control which is rendered. ASP.NET has its unique logic to generate clientids. It is very hard to predict what client id the page is going to render when it is put in the client side. ASP.NET has an unique naming system, which generates the client ids and sends to the browser based on certain logic. With the introduction of ASP.NET 4.0, the work become very easier. Handling with the client ids are now very easy.