title: Partial PostBack and actions on client side
body: <p>I've got two DropDownLists. First is visible and second is not. I'd like to have something like this:   </p>
  
  <ol>
  <li>Select value from first DDL.</li>
  <li>Then partial postback occurs - the data is retrieved from DB based on selection.</li>
  <li>Second DDL is populated</li>
  <li>Second DDL is shown with i.e. slide effect (javascript)</li>
  </ol>
  
  <p>I don't want to have full postback. The final effect should be:  </p>
  
  <p>Select value from first DDL and then below, slides down second DDL which is populated.</p>
  
  <p>I don't have a clue how to start.</p>