// From: https://developer.mozilla.org/de/docs/AJAX/Einf%C3%BChrung

var ajax = function(target, callback) {
	var http_request = false;
	
	if (window.XMLHttpRequest) { // Mozilla, Safari,...
		http_request = new XMLHttpRequest();
		if (http_request.overrideMimeType) {
			http_request.overrideMimeType('text/xml');
		}
	} else if (window.ActiveXObject) { // IE
		try {
			http_request = new ActiveXObject("Msxml2.XMLHTTP");
		} catch (e) {
			try {
				http_request = new ActiveXObject("Microsoft.XMLHTTP");
			} catch (e) {}
		}
	}
	
	if (!http_request) {
		alert('Ende :( Kann keine XMLHTTP-Instanz erzeugen');
		return false;
	}

	http_request.onreadystatechange = gotResponse;
	http_request.open('GET', target, true);
	http_request.send(null);
	
	function gotResponse() {
		if (http_request.readyState == 4) {
			if (http_request.status == 200) {
				if(callback != null) callback(http_request.responseText);
			} else {
				alert('Bei dem Request ist ein Problem aufgetreten.');
			}
		}
	}
}