function leftnav(highlight,subnav) {

	if ( highlight != '' ) {

	document.getElementById(highlight).className = 'topicon';

	}

	if ( subnav != '' ) {

    		document.getElementById(subnav).className = 'subtopicson';

  	}
	
	// if there is an optional third argument, use it to turn on a left nav item that only appears sometimes (ie. "full story")
	// the actual leftnav item should start with a class of "topichide"
	
	if (arguments.length == 3) { 
		var singlesub = arguments[2];
  	  	document.getElementById(singlesub).className = 'topicon';
	}

	// after the display options for the leftnav have been exectuted, make the whole left nav visible on the page

	document.getElementById('leftnav').style.visibility = "visible"; 

}