var xmlhttp;

function GetXmlHttpObject() {
		if (window.XMLHttpRequest)  {
  			// code for IE7+, Firefox, Chrome, Opera, Safari
		    return new XMLHttpRequest();
		}
		if (window.ActiveXObject) {
		   // code for IE6, IE5
		   return new ActiveXObject("Microsoft.XMLHTTP");
  		}
		return null;
}

function mostrarLicitacion(str) {
	xmlhttp=GetXmlHttpObject();
	if (xmlhttp==null) {
	  alert ("Browser does not support HTTP Request");
	  return;
	}
	var url="ajax.php";
	url=url+"?opc="+str;
	xmlhttp.onreadystatechange=stateChanged;
	xmlhttp.open("GET",url,true);
	xmlhttp.send(null);
}
function stateChanged() {
	if (xmlhttp.readyState==4) { document.getElementById("ajaxEstado").innerHTML=xmlhttp.responseText; }
}