/* section affected by size change is the first enclosed by tag span */
function changeFontsize(increment) 
{ var newFontSize = parseInt(document.getElementsByTagName('span')[0].style.fontSize) 
  if (isNaN(newFontSize) | increment==0) {newFontSize = parseInt(document.getElementById('sizetest').offsetHeight-2);}
  document.getElementsByTagName('span')[0].style.fontSize = newFontSize + parseInt(increment)+ 'px';
}

/* visibilty toggle by tag */
function toggle_visibility(tagname) 
{ var e = document.getElementsByTagName(tagname);
  for (i=0;i<e.length;i++) 
  { if(e[i].style.visibility == 'hidden'){e[i].style.visibility = 'visible';}
    else {e[i].style.visibility = 'hidden';}
  }
}