<script type="text/javascript">  
//Specify affected tags. Add or remove from list:  
var tgs = new Array( 'div','td','tr');  

//Specify spectrum of different font sizes:  
var szs = new Array( 'xx-small','x-small','small','medium','large','x-large','xx-large' );  
var startSz = 2;  

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 > 6 ) sz = 6;  
          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 ];  
          }  
}  
</script>

<a href="javascript:ts('body',1)">+ Больший Шрифт</a> | <a  
href="javascript:ts('body',-1)">+ Маленький Шрифт</a>