//Specify affected tags. Add or remove from list:
var tgs = new Array('div','font');

//Specify spectrum of different font sizes:
var szs = new Array( '10px','11px','12px','13px','14px','15px','16px','17px','18px','19px','20px','21px','22px','23px','24px' );
var startSz = 6;

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 > 14 ) sz = 14;
	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 ];
	}
}