//CONSTRUCTOR DE AJAX
function creaAjax()
		{
		    var xmlhttp=false;
		    try {
		    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
		    } catch (e) {
		    try {
		    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
		    } catch (E) {
		    xmlhttp = false;
		    }
		    }
		
		    if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
		    xmlhttp = new XMLHttpRequest();
		    }
		    return xmlhttp;
		}