title: How do ASP.net validation controls work?
body: <p>I am confused about client side and server side validation in ASP.net.   </p>
  
  <p>I know that client side validations validate on the client side, and <code>asp.net validation controls</code> are server side controls. But if I am applying it on any server side control like <code>&lt;asp:textbox&gt;</code> and apply <code>RequiredFieldValidator</code>, it validates immediately like a client side control. All other asp validation controls validate immediately without post back to server.  </p>
  
  <p>So how does it work without posting back to the server?</p>