if (document.images) {
  img1 = new Image();
  img1.src  = "images/knop_01.gif";
  img2 = new Image();
  img2.src  = "images/knop_02.gif";
  img3 = new Image();
  img3.src  = "images/knop_03.gif";
  img4 = new Image();
  img4.src  = "images/knop_04.gif";
  img5 = new Image();
  img5.src  = "images/knop_05.gif";

  img1r = new Image();
  img1r.src  = "images/knop_01_r.gif";
  img2r = new Image();
  img2r.src  = "images/knop_02_r.gif";
  img3r = new Image();
  img3r.src  = "images/knop_03_r.gif";
  img4r = new Image();
  img4r.src  = "images/knop_04_r.gif";
  img5r = new Image();
  img5r.src  = "images/knop_05_r.gif";

  img1s = new Image();
  img1s.src  = "images/knop_01_s.gif";
  img2s = new Image();
  img2s.src  = "images/knop_02_s.gif";
  img3s = new Image();
  img3s.src  = "images/knop_03_s.gif";
  img4s = new Image();
  img4s.src  = "images/knop_04_s.gif";
  img5s = new Image();
  img5s.src  = "images/knop_05_s.gif";
 }

function CheckSteller() {
  if (steller == 1) document.images.knop1.src = eval("img1s.src");
  if (steller == 2) document.images.knop2.src = eval("img2s.src");
  if (steller == 3) document.images.knop3.src = eval("img3s.src");
  if (steller == 4) document.images.knop4.src = eval("img4s.src");
  if (steller == 5) document.images.knop5.src = eval("img5s.src");
  }

function tempchange(Nr) {
  document.images["knop"+Nr].src = eval("img"+Nr+"r.src");
  CheckSteller();
  }

function restchange(Nr) {
  document.images["knop"+Nr].src = eval("img"+Nr+".src");
  CheckSteller();
  }

function defchange(Nr) {
  for (var i=1; i<=5; i+=1) {
    document.images["knop"+i].src = eval("img"+i+".src");
    }
  if (Nr != 0) {
    document.images["knop"+Nr].src = eval("img"+Nr+"s.src");
    }
  steller = Nr;
  CheckSteller();
  }



  function CodeM(a,b){
  	var at = "@";
  	this.location.href="mailto:"+a+at+b;
  	return false;
  }
  
  function CodeMail(u,d){
  	var at = "<img name=\""+u+"at"+"\"  src=\"images/at.gif\" border=\"0\" />";
	document.write("<a href=\"#\" onmouseover=\"return flip('"+u+"', 'down');\" onmouseout=\"return flip('"+u+"', 'up');\" onclick=\"return CodeM('"+u+"', '"+d+"');\">"+u+"<img id=\""+u+"at\" src=\"images/at.gif\" border=\"0\" align=\"middle\" onmouseover=\"flip('"+u+"', 'down');\" onmouseout=\"flip('"+u+"', 'up');\" />"+d+"</a>");
  }
  
  //flip at symbool
  //o = object
  //r = richting (up, down)
  function flip(id,r){
  	var naam = id+'at';
  	var o = document.getElementById(naam);
  		
  	if (r=="down" && o){
  		o.src = 'images/at.gif'
  	}
  	else if (r=="up" && o){
  		o.src = 'images/at.gif';
  	}
  	return true;
  }
  
function checkForm() {
	if (document.getElementById('spAnswer').value == '') {
		alert('Vergeet het antwoord (sos) op antispamvraag niet in te vullen.');
		return false;
	}
	return true;
}