title: Adding timestamp to javascript file disables caching of this file?
body: <p>I had this script in <code>&lt;head&gt;</code> of my website:</p>
  
  <pre><code>function check_messages() {
  $('#messages').load('/check.php?tt='+(new Date()).getTime(),
  function(responseText, textStatus, XMLHttpRequest) {
  if(responseText != "") {
  $("html,body").scrollTop("messages",0);
  }
  });
  }
  var auto_refresh = setInterval(check_messages, 180000);
  </code></pre>
  
  <p>Now I moved this function to external javascript file. The file is about 20 KB.</p>
  
  <p>This script contains timestamp and I want to be sure that browsers will use cached version of this javascript? Will they? I don't want them to load the whole 20 KB script again and again.</p>