title: How server side events are called in .NET
body: <p>I am a beginner to .NET, I have some doubts in my mind. Can anybody help me to sort out?</p>
  
  <ol>
  <li><p>When a user requests for a file(*.ASPX), The request first goes to IIS server and with the help of Handlers and modules it finds the type of file that need to be processed and sent back to the client. But while displaying on the cilent machine the content of the .ASPX file will be displayed as HTML controls. How are the events generated at the client side and sent back to the server?</p></li>
  <li><p>I know runat=server tells the control will be processed at serverside.
  But every time why we need to write "runat=server". Is there any ASP.NET control which runs at client side?</p></li>
  </ol>