function toonKnop(knopId){
  document.getElementById(knopId).src = "/Dordrecht/gx/ZahxronHqC.gif";
  document.getElementById(knopId).width = 16;
  document.getElementById(knopId).height = 16;
}

function openPopup(url, left, top, width, height, name, extra)
{
  if(top == '-1')
  {
    top = (0.5 * screen.availHeight) - (0.5 * height);
  }
  if(left == '-1')
  {
    left = (0.5 * screen.availWidth) - (0.5 * width); 
  }
  optionStr="toolbar=no,location=no,directories=no,status=no,menubar=no";
  if(extra=="resize")
  {
    optionStr+=",scrollbars=yes,resizable=yes";
  }
  else
  {
    optionStr+=",scrollbars=no,resizable=no";
  }
  optionStr+=",width="+width+",height="+height+",top="+top+",left="+left;
  if(name)
  {
    targ=window.open (url, name, optionStr);
  }
  else
  {
    targ=window.open (url, "", optionStr);
  }
  targ.focus();
}