var sW = screen.availWidth;
var sH = screen.availHeight;
var mX = Math.round(sW/2);
var mY = Math.round(sH/2);

function over(img){
	if(img.name != navAktiv){
		img.src = "img/buttons/"+img.name+"_over.gif";
	}
}
function out(img){
	if(img.name != navAktiv){
		img.src = "img/buttons/"+img.name+".gif";
	}
}
function klick(img){
	img.src = "img/buttons/"+img.name+"_klick.gif";
}
function popup(url,w,h){
	var xpos = mX-Math.round(w/2);
	var ypos = mY-Math.round(h/2);
	if(h>sH){
		var breite = w+16;
		var hoehe = sH-30;
		fenster = window.open(url,"fenster","width="+breite+",height="+hoehe+",left="+xpos+",top="+ypos+",scrollbars=yes");
	}else{
		var breite = w;
		var hoehe = h;
		fenster = window.open(url,"fenster","width="+breite+",height="+hoehe+",left="+xpos+",top="+ypos);
	}
	fenster.focus();
}