var isNew = 0;
var isNS4 = 0;
var isIE4 = 0;
var brow = ((navigator.appName) + parseInt(navigator.appVersion));

if (parseInt(navigator.appVersion) > 5){
	isNew = 1;
} else if (brow == "Microsoft Internet Explorer4"){
	isIE4 = 1;
} else if (brow == "Netscape4"){
	isNS4 = 1;
}

if (isNS4 || isIE4 || isNew){
	docObj = (isNS4) ? 'document' : 'document.all';
	styleObj = (isNS4) ? '' : '.style';
}

function toon (element){
  var dom;
  dom = eval (docObj + '.' + element + styleObj);
  state = dom.visibility;
  dom.visibility = "visible";
  state = dom.display;
	dom.display = "block";
}

function verberg (element){
  var dom;
  dom = eval (docObj + '.' + element + styleObj);
  state = dom.visibility;
  dom.visibility = "hidden";
  state = dom.display;
  dom.display = "none";
}


function xpopup(f,x,y){
  window.open(f,'_blank','width='+x+',height='+y+',directories=no,toolbar=no,scrollbars=yes,resizable=yes');
}


function toets(x){
   if( x > 47 && x < 58){
     y = x;
   } else {
     y = false;
   }
   return y;
}