function slide(callerObj, action, height){
	if (action== 'over'){
		callerObj.style.backgroundPosition="0px -"+height+"px";
	}
	else{
		callerObj.style.backgroundPosition="0px 0px";
	}
}
function addLoadEvent(func) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	}
	else {
		window.onload = function() {
			oldonload();
			func();
		}
	}
}