// library functions
// shorthand document.getElementById
function $(elem){
	return document.getElementById(elem);
}
// allows multiple window.onload function invocations
function addLoadEvent(func){
	var oldonload = window.onload;
	if (typeof window.onload != 'function'){
    	window.onload = func;
	} else {
		window.onload = function(){
			oldonload();
			func();
		}
	}
}
// hide/show functions - pass an element or an id of an element
function hide(elem){
	elem.style.display = 'none';
}
function show(elem){
	elem.style.display = 'block';
}
function showHide(elem){
	if(elem.style.display == 'none'){
		show(elem);
	} else {
		hide(elem);
	}
}