buttonDir = 'images/btns/';
buttonOverSuffix = '_over';
buttonExt = '.gif';

function buttonOver(button) {
	buttonObject = document.getElementById(button);
	buttonObject.src = buttonDir + button + buttonOverSuffix + buttonExt;
}

function buttonOut(button) {
	buttonObject = document.getElementById(button);
	buttonObject.src = buttonDir + button + buttonExt;
}