var sizes = [ 'xx-small','x-small','small','medium','large','x-large','xx-large' ];
var currentSize = 3;

function ts( trgt,inc ) 
{
	currentSize += inc;
	if( currentSize < 0 ) currentSize = 0;
	if( currentSize > 6 ) currentSize = 6;
	
	$('#' + trgt ).css('font-size', sizes[currentSize] );
}