The opposite pros and cons that applied to processing data validation on the user's computer apply to processing data validation on the Web server.For instance, since the validation occurs on the Web server, your application must post the Web page that the user is viewing back to the Web server for validation to occur.Validating the information entered by users is an essential part of developing a professional Web-based user interface. NET validation controls use a combination of the benefits of traditional data validation. NET data validation controls process data validation on the Web server, but you can also optionally process data validation on the user's computer. Hence, if you configure the data validation controls to enable validation on the user's computer, the resulting HTML is browser-specific.More precisely, the rendered HTML uses a script library called Web and implements Microsoft JScript functionality that is only supported by Microsoft Internet Explorer 4.0 and later versions.
Users with harmful intent may easily modify the validation script because it is contained in the source of the page that is sent to the user's computer.
In the snippet that follows I've indicated the HTML to generate both an asp: Text Box control and a linked asp: Required Field Validator control.