function cijfers(evt) 
{
  var charCode = (evt.which) ? evt.which : evt.keyCode;
  if ((charCode >= 48 && charCode <=57 ) || charCode == 8)
  { 
    return true; 
  }
  return false;
}

function nieuwsbrief_box_aan(offset)
{
  offset = offset+200;
  document.getElementById('container').style.opacity='0.2';
  document.getElementById('container').style.filter='alpha(opacity=20)';
  document.getElementById('nieuwsbrief_aanmelden').style.display='block';
  document.getElementById('nieuwsbrief_aanmelden').style.top=''+offset+'px';
}

function nieuwsbrief_box_aan2(offset)
{
  document.getElementById('container').style.opacity='0.2';
  document.getElementById('container').style.filter='alpha(opacity=20)';
  document.getElementById('nieuwsbrief_aanmelden').style.display='block';
  document.getElementById('nieuwsbrief_aanmelden').style.top='50px';
}


function nieuwsbrief_box_uit()
{
  document.getElementById('container').style.opacity='1';
  document.getElementById('container').style.filter='alpha(opacity=100)';
  document.getElementById('nieuwsbrief_aanmelden').style.display='none';
}


function getoffset(el) 
{
  var _x = 0;
  var _y = 0;
  while( el && !isNaN( el.offsetLeft ) && !isNaN( el.offsetTop ) ) {
      _x += el.offsetLeft - el.scrollLeft;
      _y += el.scrollTop;
      el = el.parentNode;
  }
  return { top: _y, left: _x };
}