// JavaScript Document
function MM_swapImgRestore() { //v3.0
  var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
}
function MM_preloadImages() { //v3.0
  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
    if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
}

function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_swapImage() { //v3.0
  var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
   if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}
function changeBG(image) {
	if (screen.width>=1950) {
		screenSize = "2600";
	} else if (screen.width>=1700) {
		screenSize = "1950";
	} else if (screen.width>=1450) {
		screenSize = "1700";
	} else if (screen.width>=1300) {
		screenSize = "1450";
	} else if (screen.width>=800) {
		screenSize = "1300";
	} else {
		screenSize = "800";
	} 
	if (document.body){
		document.body.background = "images/background/"+screenSize+"/"+image;
	}
	myHeight = document.documentElement.clientHeight;
	document.getElementById('prepage').style.height = myHeight; 
}
<!-- PreLoad Wait - Script -->
function waitPreloadPage() { //DOM
	if (document.getElementById){
		document.getElementById('prepage').style.visibility='hidden';
	} else {
		if (document.layers){ //NS4
			document.prepage.visibility = 'hidden';
		} else { //IE4
			document.all.prepage.style.visibility = 'hidden';
		}
	}
	window.clearInterval(waiter);
}
function toLongWait () {
	waitPreloadPage();
}
function MM_validateForm() { //v4.0
  if (document.getElementById){
    var i,p,q,nm,test,num,min,max,errors='',args=MM_validateForm.arguments;
    for (i=0; i<(args.length-2); i+=3) { test=args[i+2]; val=document.getElementById(args[i]);
      if (val) { nm=val.name; if ((val=val.value)!="") {
        if (test.indexOf('isEmail')!=-1) { p=val.indexOf('@');
          if (p<1 || p==(val.length-1)) errors+='- '+nm+' must contain an e-mail address.\n';
        } else if (test!='R') { num = parseFloat(val);
          if (isNaN(val)) errors+='- '+nm+' must contain a number.\n';
          if (test.indexOf('inRange') != -1) { p=test.indexOf(':');
            min=test.substring(8,p); max=test.substring(p+1);
            if (num<min || max<num) errors+='- '+nm+' must contain a number between '+min+' and '+max+'.\n';
      } } } else if (test.charAt(0) == 'R') errors += '- '+nm+' ist ein Pflichtfeld.\n'; }
    } if (errors) alert('Bitte überprüfen Sie Ihre Eingabe.');
    document.MM_returnValue = (errors == '');
} }