function byId(id) {
		return document.getElementById(id);
	}

	var resObject = null;

	function erzeugeXMLHttpRequestObject() {
		var resObject = null;
		try {
			resObject = new ActiveXObject("Microsoft.XMLHTTP");
		}
		catch(Error) {
			try {
				resObject = new ActiveXObject("MSXML2.XMLHTTP");
			}
			catch(Error) {
				try {
					resObject = new XMLHttpRequest();
				}
				catch(Error) {
					alert("Dieser Browser bietet leider keine AJAX Funktionalität");
				}
			}
		}
		return resObject;
	}

	/* AMAZON DETAILS */
	function getAmazonDetails(isbn) {
		var timestamp = new Date().getTime(); // neue url für IE vortäuschen
		resObject.open("get", "includes/getBookDetailsSmall.php?ISBN="+isbn+"&time="+timestamp, true);
		resObject.onreadystatechange = handleResponse;
		resObject.send(null);
	}

	function handleResponse() {
		if (resObject.readyState == 4) {
			var response = resObject.responseText;
			byId("ajaxcontent").innerHTML = response;
		}
		else
			byId("ajaxcontent").innerHTML = "<strong>L O A D I N G !</strong>";
	}

	/* ISBN IMAGE */
	function getImageByISBN() {
		var isbn = byId('b_isbn').value;
		if (isbn.length < 10) {
			byId('request_isbn_answer').style.display = 'inline';
			byId('request_isbn_answer').innerHTML = "<p style=\"color: red; margin-left: 10px;\"><strong>Fehler</strong>:<br /> Es werden nur 10-stellige ISBN-Nummern unterstützt!</p>";
			return false;	
		}
		var timestamp = new Date().getTime(); // neue url für IE vortäuschen
		resObject.open("get", "includes/getAmazonImage.php?ISBN="+isbn+"&time="+timestamp, true);
		resObject.onreadystatechange = handleAmazonImage;
		resObject.send(null);
	}

	function handleAmazonImage() {
		if (resObject.readyState == 4) {
			var response = resObject.responseText;
			if (response != "0") {
				var book_info = response.toString().split('||**||');
				var img = document.createElement('img');
				img.setAttribute('border', '0');
				img.setAttribute('alt', book_info[0]);
				img.setAttribute('class', 'new_book_image');
				img.setAttribute('className', 'new_book_image');
				img.setAttribute('src', book_info[3]);
				byId('request_isbn_image_answer').innerHTML = '';
				byId('request_isbn_image_answer').appendChild(img);
				byId('new_book_title').innerHTML = book_info[1];
				byId('new_book_author').innerHTML = book_info[2];
				/* set foreign book */
				byId('new_book_foreign').value = book_info[4];
				byId('request_isbn_image_answer').style.display = 'inline';
				byId('request_isbn_text_answer').style.display = 'inline';
				byId('new_book_title').style.display = 'inline';
				byId('request_isbn_answer').style.display = 'none';
			} else {
				byId('new_book_title').innerHTML = "";
				byId('new_book_author').innerHTML = "";
				byId('request_isbn_image_answer').style.display = 'none';
				byId('request_isbn_text_answer').style.display = 'none';
				byId('new_book_title').style.display = 'none';
				byId('request_isbn_answer').style.display = 'inline';
				byId('request_isbn_answer').innerHTML = "<p style=\"color: red; margin-left: 10px;\"><strong>Fehler</strong>:<br /> Leider haben wir unter dieser ISBN-Nummer kein Buch gefunden!</p>";
			}
		}
		else {
			byId("request_isbn_image_answer").innerHTML = "<strong>L O A D I N G !</strong>";
		}
	}

	/* MAKE TAG CLOUD */
	function makeTagCloud(count) {
		var timestamp = new Date().getTime(); // neue url für IE vortäuschen
		resObject.open("get", "includes/make_tag_cloud.php?count="+count+"&time="+timestamp, true);
		resObject.onreadystatechange = handleTagCloud;
		resObject.send(null);
	}

	function handleTagCloud() {
		if (resObject.readyState == 4) {
			var response = resObject.responseText;
			byId("ajaxcontent").innerHTML = response;
		}
		else
			byId("ajaxcontent").innerHTML = "<div class=\"ajax_loading\"><img src=\"images/loading.gif\" border=\"0\"></div>";
	}


	resObject = erzeugeXMLHttpRequestObject();