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

//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 ];
        }
}