function chgImg(imageName, chgImagePath) {
	document[imageName].src = chgImagePath;
}

function onImg(imageName) {
	fileName = document[imageName].src;
	fileName = fileName.substring(0, fileName.length - 4);
	document[imageName].src = fileName + "_on.gif";
}

function offImg(imageName) {
	fileName = document[imageName].src;
	fileName = fileName.substring(0, fileName.length - 7);
	document[imageName].src = fileName + ".gif";
}