function on1() 
{if (!document.images) return; document.a.src = "images/werkwijze_on.jpg";} 
function on2() 
{if (!document.images) return; document.b.src = "images/vestigingen_on.jpg";}
function on3() 
{if (!document.images) return; document.c.src = "images/home_on.jpg";}
function on4() 
{if (!document.images) return; document.d.src = "images/contact_on.jpg";}
function off1() 
{if (!document.images) return; document.a.src = "images/werkwijze_off.jpg";}
function off2() 
{if (!document.images) return; document.b.src = "images/vestigingen_off.jpg";}
function off3() 
{if (!document.images) return; document.c.src = "images/home_off.jpg";}
function off4() 
{if (!document.images) return; document.d.src = "images/contact_off.jpg";}

var imgslist = new Array(
"images/werkwijze_on.jpg",
"images/werkwijze_off.jpg",
"images/vestigingen_on.jpg",
"images/vestigingen_off.jpg",
"images/home_on.jpg",
"images/home_off.jpg",
"images/contact_on.jpg",
"images/contact_off.jpg"); 

var imgs=new Array(); 
for (x=0; x<imgslist.length; x++) 
 if (document.images) 
  {imgs[x]=new Image(); imgs[x].src = imgslist[x];}