window.onload = showImage;

function showImage() { // U.H. v1.0
  if (!document.getElementsByTagName) return true;
    var allImages = document.getElementsByTagName("img");
    for (var i=0, anImage; anImage=allImages[i]; i++) {
		if (anImage.className == "show") {
			var bigImageBox = document.getElementById("bildgross");
    		anImage.onclick = function() {
				bigImageBox.innerHTML = '<img src="' + this.parentNode.href + '" />'; 
    			return false;
    		}
    		anImage.parentNode.onfocus = function() {
				bigImageBox.innerHTML = '<img src="' + this.href + '" />'; 
    			return false;
    		}
		}
    }
}