function toggleDisplay(objId,showDisplay){
        var tObj = document.getElementById(objId);

	if (!showDisplay) {
		 showDisplay = 'block';
	}

        if (tObj.style.display == 'none') {
                tObj.style.display = showDisplay;
        } else if (tObj.style.display == showDisplay) {
                tObj.style.display = 'block';
        } else {
		tObj.style.display = showDisplay;
	}
}


/**
* within a set of buttons, display and hide the rest
*/
function switchDisplay(objIdOn, objIdOff1, objIdOff2){
	toggleDisplay(objIdOn,'block');	
	toggleDisplay(objIdOff1,'none');	
	toggleDisplay(objIdOff2,'none');	
}