if (document.images) {
image1on = new Image();
image1on.src = "images/2d2.png";
image1off = new Image();
image1off.src = "images/2d1.png";

image2on = new Image();
image2on.src = "images/2dwerkwijze2.png";
image2off = new Image();
image2off.src = "images/2dwerkwijze1.png";

image3on = new Image();
image3on.src = "images/con2.png";
image3off = new Image();
image3off.src = "images/con1.png";

image4on = new Image();
image4on.src = "images/port2.png";
image4off = new Image();
image4off.src = "images/port1.png";

image5on = new Image();
image5on.src = "images/seo2.png";
image5off = new Image();
image5off.src = "images/seo1.png";

} 
function changeImages() {
if (document.images) {
for (var i=0; i<changeImages.arguments.length; i+=2) {
document[changeImages.arguments[i]].src = eval(changeImages.arguments[i+1] + ".src");
}}}