Salve a tutti, io non riesco a capire come mai il mio AJAX non funziona:

riporto il codice js:
function Inint_AJAX() {
try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch(e) {} //IE
try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch(e) {} //IE
try { return new XMLHttpRequest(); } catch(e) {} //Native Javascript
alert("XMLHttpRequest not supported");
return null;
}

function dochange(src, val) {
var req = Inint_AJAX();
req.onreadystatechange = function () {
if (req.readyState==4) {
if (req.status==200) {
document.getElementById(src).innerHTML=req.respons eText;
}
}
};
req.open("GET", "search_ajax.php?data="+src+"&val="+val);
req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8");
req.send(null);
}

window.onLoad=dochange('province', -1);
e il codice del FORM:
.......
<form>
<div class="clear"></div>
<div class="block">
<label>Country</label>
<?php
echo "<div id=province><select >\n";
echo "<option value='0'>============</option> \n" ;
echo "</select></div>";
?>
.......
Non entra neanche in search_ajax.php , come mai? problema di ID?