function preloadImages() {
	if (document.images){
	var btn_studentarea_roll = new Image
		btn_studentarea_roll.src = "../images/btn_studentarea_over.gif"
	var btn_teacherarea_roll = new Image
		btn_teacherarea_roll.src = "../images/btn_teacherarea_over.gif"
	var btn_aboutproject_roll = new Image
		btn_aboutproject_roll.src = "../images/btn_aboutproject_over.gif"
	var btn_credits_roll = new Image
		btn_credits_roll.src = "../images/btn_credits_over.gif"
	var btn_bibliography_roll = new Image
		btn_bibliography_roll.src = "../images/btn_bibliography_over.gif"
	var btn_contactus_roll = new Image
		btn_contactus_roll.src = "../images/btn_contactus_over.gif"
	var btn_go_roll = new Image();
		btn_go_roll.src = "../images/btn_go_over.gif";
	var btn_getkey_roll = new Image();
		btn_getkey_roll.src = "../images/btn_getkey_over.gif";
	var btn_continue_roll = new Image();
		btn_continue_roll.src = "../images/btn_continue_over.gif";
	}
}

function changeImages(sName,sImage)
	{
	if (document.images)
		{
		document.images[sName].src = sImage;
		}
	}

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

function closeWindow()
	{
	window.close();
	}

if (document.layers)
	{
	origWidth = innerWidth;
	origHeight = innerHeight;
	}
function reloadPage()
	{
	if (innerWidth != origWidth || innerHeight != origHeight)
	location.reload();
	}
if (document.layers)
	onresize=reloadPage;
	
function goHistory()
	{
	window.history.go(-1);
	}
	
function getCurrDate()
	{
	currDate=new Date();
	currYear = currDate.getFullYear();
	if (currYear<2000)
		{
		currYear+=1900;
		}
	}