function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}

// dom scripting, p. 285f
addLoadEvent(prepareForms);
function prepareForms(){
	for (var i=0; i<document.forms.length; i++) {
		var thisform = document.forms[i];
		resetFields(thisform);
		thisform.onsubmit = function() {
			return validateFields(this);
		}
	}
}

/*
	fragt in jeder form die default-werte der input-felder ab, 
	macht bei onfocus das input-feld leer und 
	bei onblur wieder den alten text rein...
*/
function resetFields(whichform){
	for (var i=0; i<whichform.elements.length; i++) {
		var element = whichform.elements[i];
		if (element.type == "submit") continue;
		if (!element.defaultValue) continue;
		
		element.onfocus = function(){
			if (this.value == this.defaultValue) {
				this.value = "";
			}
		}
		
		element.onblur = function() {
			if (this.value == "") {
				this.value = this.defaultValue;
			}
		}
	}
}

// macht das suchfeld sichtbar/unsichtbar
document.write("<style type='text/css'>form#searchform {display:none;}</style>");

function anzeigen(element){
	if (!document.getElementById) return false;
	if (!document.getElementById(element)) return false;
	var ele = document.getElementById(element);
	if (ele.style.display != "block"){
		ele.style.display = "block";
	} else {
		ele.style.display = "none";
	}
}

// http://www.maratz.com/blog/archives/2006/05/22/smart-back-to-top-link/
// top-scroll-link wird nur sichtbar, wenn das browser-fenster zu klein ist...
var d = document;
function topLinksichtbar(){
	var viewport_height = (self.innerHeight) ? self.innerHeight : (document.documentElement && document.documentElement.clientHeight) ? document.documentElement.clientHeight : (document.body) ? document.body.clientHeight : 0;
	var page_height = d.getElementsByTagName('body')[0].offsetHeight;
	if (!document.getElementById('top')) return false;
	var ttl = d.getElementById('top');
	if (page_height < viewport_height) ttl.style.visibility = 'hidden';
}
addLoadEvent(topLinksichtbar);