function roll_on(imgName){
	if(document.images)
		document[imgName].src = 'images/' + imgName + '_on.gif';
}

function roll_off(imgName){
	if(document.images)
		document[imgName].src = 'images/' + imgName + '.gif';
}

function openWindow(theURL,winName,features) { 
	window.open(theURL,winName,features);
}