var xmlHttp = null;
var activeContext = null;

// Mozilla, Opera, Safari sowie Internet Explorer (ab v7)
if (typeof XMLHttpRequest != 'undefined') {
	xmlHttp = new XMLHttpRequest();
}

if (!xmlHttp) {
	// Internet Explorer 6 und älter
	try {
		xmlHttp  = new ActiveXObject("Msxml2.XMLHTTP");
	} catch(e) {
		try {
			xmlHttp  = new ActiveXObject("Microsoft.XMLHTTP");
		} catch(e) {
			xmlHttp  = null;
		}
	}
}

// start with welcome page as initial context
function initPage() {
	change_context("willkommen");
}

function change_context(context,pagenumber) {
	xmlHttp.open('GET', './content.xml.php?context='+context+'&pagenumber='+pagenumber, true);
	xmlHttp.onreadystatechange = function () {

	if (xmlHttp.readyState == 4) {

		var xml = xmlHttp.responseXML;

		var i,id,element,attr = null;

		// highlight context in navigation
		if(activeContext != null && activeContext != "impressum")
			document.getElementById(activeContext).innerHTML =
			"<img src='./images/"+activeContext+"_inaktiv.png' alt='"+activeContext+"' />";

		if(context != "impressum")
			document.getElementById(context).innerHTML =
			"<img src='./images/"+context+"_aktiv.png' alt='"+context+"' />";

		activeContext = context;

		// change look and content of the divs from xml
		var divTags = document.getElementsByTagName("div");
		for(i = 0; i < divTags.length; i++) {

			id = divTags[i].id;

			// empty root tag check for iexplore
			if(id != "") {
				if(element = xml.getElementsByTagName(id).item(0)) {

					if(attr = element.getAttribute("width"))
						divTags[i].style.width = attr;

					if(attr = element.getAttribute("height"))
						divTags[i].style.height = attr;

					if(attr = element.getAttribute("bgimage"))
						divTags[i].style.backgroundImage = attr;

					if(element.hasChildNodes())
						divTags[i].innerHTML = element.firstChild.data;
					else
						divTags[i].innerHTML = "";
				}
			}
		}
	}
	};
	xmlHttp.send(null);
}