Client side validation

How to show validation message in the same page we send request through.For instance, we fill up registration details in a

registration page and click submit button.Then we see the same page with some message(Like you have not entered your

address or you have entered invalid phone no.) and showing the same values what we selected before submitting in the form

fields.please tell me source codes of how to accomplish the above thing and do client level validation.

[493 byte] By [Vinodbhai@suna] at [2007-11-27 5:12:08]