if(screen.availWidth)
  {
   breedte = screen.availWidth;
  }
 else
  {
   breedte = document.body.clientWidth;
  }

 if(breedte<=1024)
  {
   stylesheet = '../css/style_1024_768.css';
  }

 else if(breedte<=1152)
  {
   stylesheet = '../css/style_1152.css';
  }
  else if(breedte<=1280)
  {
   stylesheet = '../css/style_1280.css';
  }
  else if(breedte<=1680)
  {
   stylesheet = '../css/style_1680.css'
  }
  else if(breedte<=1920)
  {
   stylesheet = '../css/style_big.css';
  }
 
 else 
  {
   stylesheet = '../css/style_1280.css';
  }

  /* menu */
  function setVisibility(id, visibility){
	document.getElementById(id).style.display = visibility;
 }