var tgs = new Array( 'div','td','tr');
var szs = new Array( '8px','10px','12px','14px','16px','18px','20px' );
var startSz = 2;
function ts(inc) {
  if (!document.getElementById) return
  var d = document,cEl = null,sz = startSz,i,j,cTags;
  
  sz += inc;
  if ( sz < 0 ) sz = 0;
  if ( sz > 6 ) sz = 6;
  startSz = sz;
	
  cEl = d.body;
  cEl.style.fontSize = szs[ sz ];

  for ( i = 0 ; i < tgs.length ; i++ ) {
	cTags = cEl.getElementsByTagName( tgs[ i ] );
	for ( j = 0 ; j < cTags.length ; j++ ) cTags[ j ].style.fontSize = szs[ sz ];
  }
}