XMLHttpRequestObject = false;
	if(window.XMLHttpRequest){
			XMLHttpRequestObject = new XMLHttpRequest();
			//alert("Este browser es Firefox");
		} else if(window.ActiveXObject) {
			XMLHttpRequestObject= new ActiveXObject("Microsoft.XMLHTTP")
			}
			
			function getOptions(marc) {
			
			
				if(XMLHttpRequestObject) {
					var rand_no = Math.random();

				XMLHttpRequestObject.open("GET","xmlCreator.php?marca="+marc+"&r="+rand_no);
				
					XMLHttpRequestObject.onreadystatechange = function () {
						if(XMLHttpRequestObject.readyState == 4 && XMLHttpRequestObject.status == 200 ) {
							var xmlDocument = XMLHttpRequestObject.responseXML;
							optionst = xmlDocument.getElementsByTagName("option");
						listOptions();
						}
					}
					XMLHttpRequestObject.send(null);
				}
			}
			////////////// aqui enlisto la funcion de list options
			function listOptions() {
					
			///// borra todos los registros del drop down
			for (i = document.getElementById('optionList').length; i > 0; i--){
				document.getElementById('optionList').options[i-1] = null
				}
				////////////////////////
				var loopIndex;
				var selectControl = document.getElementById('optionList');
					for(loopIndex = 0; loopIndex < optionst.length;  loopIndex++) {
					selectControl.options[loopIndex] = new Option(optionst[loopIndex].firstChild.data);
					}
			}