function showhide(divid, but) {
obj = document.getElementById(divid);
obj.style.display = obj.style.display == 'none' ? 'block' : 'none';

imgName = obj.style.display == 'none' ?  "images/ic_ausklappen.png" : "images/ic_einklappen.png";
var newImage = "url("+imgName+")";
but.style.backgroundImage = newImage;
but.style.backgroundRepeat ="no-repeat";
but.style.backgroundPosition="top right";
}