var http = false;

if(navigator.appName == "Microsoft Internet Explorer") {
  http = new ActiveXObject("Microsoft.XMLHTTP");
} else {
  http = new XMLHttpRequest();
}

function validate() {
var fooElement = document.getElementById('adv');
  
  http.abort();
  http.open("GET", "/_js/ajaxvalidate.php?advDisplay="+fooElement.style.display, true);
  http.send(null);
  
  if (fooElement.style.display !== 'none')
  {
  fooElement.style.display = 'none';
  }
  else
  {
  fooElement.style.display = '';
  }
}