if (document.images)
   {
     pic1on= new Image(164,34);
     pic1on.src="http://www.alfabest.nl/images/overknop-home.gif";  
     pic2on= new Image(164,42);
     pic2on.src="http://www.alfabest.nl/images/overknop-producten.gif"; 
     pic3on= new Image(164,42);
     pic3on.src="http://www.alfabest.nl/images/overknop-referenties.gif"; 
     pic4on= new Image(164,42);
     pic4on.src="http://www.alfabest.nl/images/overknop-contact.gif";
	 pic5on= new Image(164,42);
     pic5on.src="http://www.alfabest.nl/images/overknop-service.gif";

     pic1off= new Image(164,34);
     pic1off.src="http://www.alfabest.nl/images/knop-home.gif";
     pic2off= new Image(164,42);
     pic2off.src="http://www.alfabest.nl/images/knop-producten.gif";
     pic3off= new Image(164,42);
     pic3off.src="http://www.alfabest.nl/images/knop-referenties.gif";
     pic4off= new Image(164,42);
     pic4off.src="http://www.alfabest.nl/images/knop-contact.gif";
	 pic5off= new Image(164,42);
     pic5off.src="http://www.alfabest.nl/images/knop-service.gif";
   }

function lightup(imgName)
 {
   if (document.images)
    {
      imgOn=eval(imgName + "on.src");
      document[imgName].src= imgOn;
    }
 }

function turnoff(imgName)
 {
   if (document.images)
    {
      imgOff=eval(imgName + "off.src");
      document[imgName].src= imgOff;
    }
 }