<script type="text/javascript">
      sniffBrowserType();
      //Shows loading.. screen
      showLoadScreen();
      //Set the javascript timer and
      //loads user list and messages
      setTimers();
      setFocus('mytext');
</script>
当用户键入一些信息并回车时，就会调用下面的函数：

<input type="text" class="mytext"
       id="mytext" onkeydown="captureReturn(event)">

// Capture the enter key on the input box and post message
function captureReturn( event )
{
      if(event.which || event.keyCode)
      {
            if ((event.which == 13) || (event.keyCode == 13))
            {
                  postText();
                  return false;
            }
            else {
                  return true;
            }
      }    
}
function postText()
{
      rnd++;
      //Clear text box first
      chatbox = getElement( "mytext" );
      chat = chatbox.value;
      chatbox.value = "";
     
      //get user GUID from url
      userid = location.search.substring( 1, location.search.length );
     
      //construct Ajax Server URL
      url = 'Server.aspx?action=PostMsg&u=' + userid + '&t=' +
             encodeURIComponent(chat) + '&session=' + rnd;
     
      //Create and set the instance
      //of appropriate XMLHTTP Request      object
      req = getAjax();
     
      //Update page with new message
      req.onreadystatechange = function(){
     
            if( req.readyState == 4 && req.status == 200 ) {
                  updateAll();
            }
      }
     
      req.open( 'GET', url, true );
      req.send( null );
}
就这么多，没什么特别的，你可以看源代码，里面有很多注释信息。