var tgs = new Array( 'div','td','tr');
var szs = new Array( 'small','medium' );
var startSz = -1;

function ts( trgt,inc ) {
      if (!document.getElementById) return
      var d = document,cEl = null,sz = startSz,i,j,cTags;
       
      sz += inc;
      if ( sz < 0 ) sz = 0;
      if ( sz > 1 ) sz = 0;
      startSz = sz;
           
      if ( !( cEl = d.getElementById( trgt ) ) ) cEl = d.getElementsByTagName( trgt )[ 0 ];

      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 ];
      }
}