var http_request = null; 

if (window.XMLHttpRequest) {
	http_request = new XMLHttpRequest();
	if (http_request.overrideMimeType) {
		http_request.overrideMimeType('text/xml');
	}
} else if (window.ActiveXObject) {
	try {
		http_request = new ActiveXObject("Msxml2.XMLHTTP");
	} catch (e)	{
		try {
			http_request = new ActiveXObject("Microsoft.XMLHTTP");
		} catch (e) {}
	}
}