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_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_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 bepaalhoogte_centerdiv() {

var divh = document.getElementById('contentdiv2').offsetHeight;
var div2h = document.getElementById('links').offsetHeight;
	if (divh > div2h) {
	document.getElementById('centerdiv').style.height = divh + "px";
	}
	if (divh < div2h) {
	document.getElementById('centerdiv').style.height = div2h + "px";
	}
 }

function bepaalhoogte_welkom() {
var div_welkomh = document.getElementById('welkom').offsetHeight;
	if (div_welkomh > 250) {
	document.getElementById('index_boven').style.height = div_welkomh + "px";
	document.getElementById('half_banner').style.height = div_welkomh + "px";
	}
}


function checkForm(form){
	if(form.naam.value == ""){
		form.naam.focus();
		alert("Fout: U heeft geen naam ingevuld.");
		return false;
	}

	if(form.adres.value == ""){
		form.adres.focus();
		alert("Fout: U heeft geen adres ingevuld.");
		return false;
	}

	if(form.postcode.value == ""){
		form.postcode.focus();
		alert("Fout: U heeft geen postcode ingevuld.");
		return false;
	}

	if(form.telefoon.value == ""){
		form.telefoon.focus();
		alert("Fout: U heeft geen telefoonnummer ingevuld.");
		return false;
	}
	
	if(form.vestiging.value == ""){
		form.vestiging.focus();
		alert("Fout: U heeft geen bestemming ingevuld.");
		return false;
	}

	if(form.email.value == ""){
		form.email.focus();
		alert("Fout: U heeft geen e-mail adres ingevuld.");
		return false;
	}
return true;
}

<!--
  function snd(form)
  {
    if (form.naam.value=="" || form.voorletters.value=="" || form.adres.value=="" || form.postcode.value=="" || form.plaats.value=="" || form.telefoon.value=="" || form.email.value=="")
    {
      alert("U heeft niet alle verplichte gegevens ingevuld");
      return false;
    }
    form.submit();
    return true;
  }
//-->