var lastButtonId="buttonHome"; //"var" niet opnieuw gebruiken voor deze variabele

      function activeButton(buttonId) {
         document.getElementById(lastButtonId).style.backgroundImage="";
         switch(buttonId) {
            case "buttonHome":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonHome.jpg)";
            break;
            case "buttonProfiel":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonProfiel.jpg)";
            break;
            case "buttonActiviteiten":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonActiviteiten.jpg)";
            break;
            case "buttonOpdrachtgevers":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonOpdrachtgevers.jpg)";
            break;
            case "buttonContact":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonContact.jpg)";
            break;
            case "buttonPortfolio":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonPortfolio.jpg)";
            break;
            case "buttonWeblog":
               document.getElementById(buttonId).style.backgroundImage="url(GRFX/buttonWeblog.jpg)";
            break;
            default:
         }
         lastButtonId=buttonId;
      }

      function changeSize(){
         var h=document.body.clientHeight;
         var w=document.body.clientWidth;
         var row1="100px";
         var row2="600px";
         var col="698px";

         //h=800 t/m ...
         if (h>799) {
            row1="100px";
            row2="600px";
         }
         //h=799 t/m 725
         else if (h<800 && h>724) {
            row1=100-(800-h)+"px";
            row2="600px";
         }
         //h=724 t/m 225
         else if (h<725 && h>224) {
            row1="25px";
            row2=600-(725-h)+"px";
            col=(698-17)+"px";
         }
         //h=0 t/m 224
         else if (h<225) {
            row1="25px";
            row2="100px";
            col=(698-17)+"px";
         }
         document.getElementById("divRow1").style.height=row1;
         document.getElementById("divRow2").style.height=row2;
         document.getElementById("ifrContent").style.width=col; //breedte wijzigen ivm scrollbalk
         document.getElementById("divMenuBelow").style.width=col; //breedte wijzigen ivm scrollbalk

         //document.getElementById("divMenuAbove").innerHTML="h: "+h+" w: "+w+" col: "+col;

         //voor sommige browsers moet tussen overflow auto en hidden geswitcht worden
         //als de hoogte van de box verandert
         if (h<725) {
            document.getElementById("divContent").style.overflow="auto";
         }
         else {
            document.getElementById("divContent").style.overflow="hidden";
         }
      }

      /*var c=0;
      var wl;
      function getIframe() {
         c=c+1;
         wl=window.location.href;
         id=document.getElementsByTagName("iframe")[0].id;
         x=document.getElementById("ifrContent");
         document.getElementById("divMenuAbove").innerHTML=x.src + c + " " + wl + " id:" + id;
         t=setTimeout("getIframe()",1000);
      }*/