var url = "provinces.php"; 
function fetchprovinces() {
  new Ajax.Request(url, {
      method: 'get',
      parameters: {cat: document.getElementById('cat').value },
      onSuccess: process,
      onFailure: function() { 
      alert("There was an error with the connection"); 
    }
  });
}

 function process(transport) {
  var response = transport.responseText;
  var div_obj = document.getElementById('province');
  div_obj.innerHTML = response;  
}