http_request = false;
 
if (window.XMLHttpRequest) 
{ 
	http_request = new XMLHttpRequest();
} 
else if (window.ActiveXObject) 
{
	try 
	{
		http_request = new ActiveXObject("Msxml2.XMLHTTP");
	} 
	catch (e) 
	{ 
		try 
		{
			http_request = new ActiveXObject("Microsoft.XMLHTTP");
		} 
		catch (e) 
		{
			alert('Ende :( Kann keine XMLHTTP-Instanz erzeugen');
		}
	}
}
if (!http_request) 
{ 
	alert('Ende :( Kann keine XMLHTTP-Instanz erzeugen');
}