function newImage(arg)
{
    if (document.images)
    {
	    rslt = new Image();
        rslt.src = arg;
		return rslt;
	}
}

function changeImages()
{
	if (document.images && (preloadFlag == true))
	{
        for (var i=0; i<changeImages.arguments.length; i+=2)
        {
			document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
		}
	}
}

var preloadFlag = false;
function preloadImages()
{
	if (document.images)
	{
		mainmenu_about_over = newImage("graphics/mainmenu_aboutButton_over.jpg");
		mainmenu_calendar_over = newImage("graphics/mainmenu_calendarButton_over.jpg");
		mainmenu_course_over = newImage("graphics/mainmenu_coursesButton_over.jpg");
		mainmenu_online_over = newImage("graphics/mainmenu_onlineButton_over.jpg");
		mainmenu_inhouse_over = newImage("graphics/mainmenu_inhouseButton_over.jpg");
		mainmenu_register_over = newImage("graphics/mainmenu_registerButton_over.jpg");
		moreinfo_1_over = newImage("graphics/moreinfo_1_over.jpg");
		moreinfo_2_over = newImage("graphics/moreinfo_2_over.jpg");
        preloadFlag = true;
	}
}