function is_numeric( mixed_var ) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: David
    // +   improved by: taith
    // +   bugfixed by: Tim de Koning
    // *     example 1: is_numeric(186.31);
    // *     returns 1: true
    // *     example 2: is_numeric('Kevin van Zonneveld');
    // *     returns 2: false
    // *     example 3: is_numeric('+186.31e2');
    // *     returns 3: true
    // *     example 4: is_numeric('');
    // *     returns 4: false

    if (mixed_var === '') {
        return false;
    }

    return !isNaN(mixed_var * 1);
}

function checkValue(name)
{
  el = eval("document.shop."+name);
  if(!is_numeric(el.value))
  {
    el.value = "0";
  }
}

function getPrice()
{
  var artikel = getElementsByClassName('shopValue');
  var summe = 0;
  var mwst = 0;
  for(i=0;i<artikel.length;i++)
  {
    priceField = artikel[i].name;
    priceField = SuchenUndErsetzen(priceField,"artikelID_","preis_");
    mwstField = SuchenUndErsetzen(priceField,"preis_","mwst_");
    summe = summe + (artikel[i].value * eval("document.shop."+priceField+".value"));
    if(artikel[i].value == "") { artikel[i].value = 0; }
    
    mwst = mwst + (((artikel[i].value * eval("document.shop."+priceField+".value")) * eval("document.shop."+mwstField+".value")) / 100 );
  }
  
  shipping = SuchenUndErsetzen(document.shop.shipping.value,",",".");
  document.shop.presumme.value = number_format(summe,2,",",".");
  
  document.shop.mwst.value = number_format(mwst,2,",",".");
  
  summe = summe + parseInt(shipping);
  document.shop.summe.value = number_format(summe,2,",",".");
}


function SuchenUndErsetzen(QuellText, SuchText, ErsatzText)
{   
  // Erstellt von Ralf Pfeifer
  // Fehlerpruefung
  
  if ((QuellText == null) || (SuchText == null))           { return null; }
  if ((QuellText.length == 0) || (SuchText.length == 0))   { return QuellText; }

  // Kein ErsatzText ?
  if ((ErsatzText == null) || (ErsatzText.length == 0))    { ErsatzText = ""; }

  var LaengeSuchText = SuchText.length;
  var LaengeErsatzText = ErsatzText.length;
  var Pos = QuellText.indexOf(SuchText, 0);

  while (Pos >= 0)
  {
      QuellText = QuellText.substring(0, Pos) + ErsatzText + QuellText.substring(Pos + LaengeSuchText);
      Pos = QuellText.indexOf(SuchText, Pos + LaengeErsatzText);
  }
  
  return QuellText;
}

function number_format(number, decimals, dec_point, thousands_sep)
{
  number = (number+'').replace(',', '').replace(' ', '');
  var n = !isFinite(+number) ? 0 : +number, 
      prec = !isFinite(+decimals) ? 0 : Math.abs(decimals),
      sep = (typeof thousands_sep === 'undefined') ? ',' : thousands_sep,        dec = (typeof dec_point === 'undefined') ? '.' : dec_point,
      s = '',
      toFixedFix = function (n, prec) {
          var k = Math.pow(10, prec);
          return '' + Math.round(n * k) / k;        };
  // Fix for IE parseFloat(0.55).toFixed(0) = 0;
  s = (prec ? toFixedFix(n, prec) : '' + Math.round(n)).split('.');
  if (s[0].length > 3) {
      s[0] = s[0].replace(/\B(?=(?:\d{3})+(?!\d))/g, sep);    }
  if ((s[1] || '').length < prec) {
      s[1] = s[1] || '';
      s[1] += new Array(prec - s[1].length + 1).join('0');
  }    return s.join(dec);
}

function getElementsByClassName(className, tag, elm){
	var testClass = new RegExp("(^|\\s)" + className + "(\\s|$)");
	var tag = tag || "*";
	var elm = elm || document;
	var elements = (tag == "*" && elm.all)? elm.all : elm.getElementsByTagName(tag);
	var returnElements = [];
	var current;
	var length = elements.length;
	for(var i=0; i<length; i++){
		current = elements[i];
		if(testClass.test(current.className)){
			returnElements.push(current);
		}
	}
	return returnElements;
}


/*

var height_left = document.getElementById("left").offsetHeight;
var height_center = document.getElementById("center").offsetHeight;
var height_right = document.getElementById("right").offsetHeight;

if(height_left > height_center && height_left > height_right)
{
	document.getElementById("left").style.height = height_left+"px";
	document.getElementById("center").style.height = height_left+100+"px";
	document.getElementById("right").style.height = height_left+100+"px";
}

if(height_center > height_left && height_center > height_right)
{
	document.getElementById("left").style.height = height_center+"px";
	document.getElementById("center").style.height = height_center+100+"px";
	document.getElementById("right").style.height = height_center+100+"px";
}

if(height_right > height_center && height_right > height_left)
{
	document.getElementById("left").style.height = height_right+"px";
	document.getElementById("center").style.height = height_right+100+"px";
	document.getElementById("right").style.height = height_right+100+"px";
}

*/