Server-side validation incorporates code validation into a form handler. NET application on the server that provides the functionality that your form needs for processing after a customer has submitted it.
Because the code is stored on the server, server-side validation requires a roundtrip to the server.
In order to access your form fields in code, you need to assign names to the form and each of the fields. For more information see, NAME Attribute | name Property.
Client-side validation provides validation within the browser on client computers through Java Script.Because the code is stored within the page or within a linked file, it is downloaded into the browser when a user accesses the page and, therefore, doesn't require a roundtrip to the server.For this reason, client form validation can be faster than server-side validation.Microsoft® Office Front Page® 2003 allows you to create some custom validation within the form feature.