XMLHttpRequest since IE 7

http://tinyurl.com/36r6y

if (window.XMLHttpRequest){

// If IE7, Mozilla, Safari, etc: Use native object
var xmlHttp = new XMLHttpRequest()

}
else
{
if (window.ActiveXObject){

// ...otherwise, use the ActiveX control for IE5.x and IE6
var xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}

}