AJAX not working with Firefox

[PeejAvery]

Well, you aren't returning the ro object. If there is no return, you can't set a variable equal to a function.

function createRequestObject() {
  var ro;
  try {ro = new XMLHttpRequest();}
  catch(e) {
    try {ro = new ActiveXObject("Msxml2.XMLHTTP");}
    catch(e) {
      try {ro = new ActiveXObject("Microsoft.XMLHTTP");}
      catch(e) {
        alert("Your browser does not support AJAX!");
        return false;
      }
    }
  }
  return ro;
}

var http = createRequestObject();