[jQuery] ajax loading image and fadeIn content

[led]

Hi, i'm just starting in jquery and i need help on this code.
I just need to display a message (or image)before the content is
loaded and fade that content.
Here is the code, and you can see it in action on realferias.com and
click the OK button on the left.Thanks.

$(document).ready(function() {
 $('#foo').click(function() {

  $('#centro').empty();

  $('#centro').fadeIn("slow").load('results_casa_mes.asp',{ nm_mes:
document.getElementById('teste4').value, pessoas:
document.getElementById('pessoas').value, tipo: document.getElementById
('tipo').value, localidade: document.getElementById
('localidade').value });
  });

 });

  $(function()
{
   $('#centro').ajaxSend(function(e,r,s)
   {
      $(this).append("<li>Starting request  </li>");
   });

});