Validations client side or server side ???

Where should the validations (Required field, range, etc.) be done in an web page client side or server side?
 As per my knowledge most of the validations are on client side using javascript, unfortunately it won't work if someone has disabled their browsers javascript option. what do we do in this case? Any suggestion please.

Both...
Client-side for rich client experience.
Server-side for data validation and for clients who have disabled javascript.

*Always* validate on the server side. You will still get the benefits of client-side validation on browsers setup to handle that. (In ASP.NET 1.x, only Internet Explorer for Windows and Mac provide client-side validation.)
See this article to learn more about this and other facts on validators: http://aspalliance.com/699. 
--- Peter Blum
Creator of Peter's Data Entry Suite (formerly Professional Validation And More and Peter's Date Package) and Peter's Polling Package
www.PeterBlum.com