It was a lot easier to understand the difference between these forms of validation when you coded Active Server Pages 3.0 because, as the programmer, you personally performed almost all data validation.You yourself either programmed it to be client-side or server-side.Validation is testing to determine whether the user entered into the field.
You must understand these two different ways of validating the data users input into a Web form.
After the user enters data into a Web form, clicks the Submit button, and sends the form data to the server as a request, you can perform server-side validation on the data.
Validation server controls are a series of controls that help you validate the data that the user enters into the other controls that are provided with ASP. They determine whether the form can be processed based upon the rules that you define in the validation server controls.
One of the most common elements of Web pages is a form in which the user can input data that is posted back to the server.
From there, you can compare user input in different fields or against values that might be held in other repositories, such as a database.