toctop1on = new Image; 
toctop1on.src = "https://www.mooswaldblick.de/clips/but_kontakt_mo.gif"
toctop1off = new Image; 
toctop1off.src="https://www.mooswaldblick.de/clips/but_kontakt.gif";

toctop2on = new Image; 
toctop2on.src = "https://www.mooswaldblick.de/clips/but_impressum_mo.gif";
toctop2off = new Image; 
toctop2off.src = "https://www.mooswaldblick.de/clips/but_impressum.gif";

function img_act(imgName)   {
	if (document.getElementById)  {
		imgOn = eval(imgName + "on.src"); 
		document.getElementById(imgName).src = imgOn;
	}
}

function img_inact(imgName)  { 
	if (document.getElementById)  {
		imgOff = eval(imgName + "off.src");
		document.getElementById(imgName).src = imgOff;
	}
}