title: Handle "File save as" event in JS
body: <p>I need:
  1) Get data from server by button click. (can ajax) 
  2) Execute some js depending on the received data.
  3) Show standard "File save as" dialog.<br>
  It must work in IE7/IE8/FF.</p>
  
  <p>Thanks! And sorry for my crooked english =)</p>