function preload(imgObj,imgSrc) {
	if (document.images) {
		eval(imgObj+' = new Image()')
		eval(imgObj+'.src = "'+imgSrc+'"')
	}
}
function changeImage(imgName,imgObj) {
	document.images[imgName].src = eval(imgObj+".src")
}
preload('imageHistoryOn','images/nav_history_on.gif');
preload('imageHistoryOff','images/nav_history_off.gif');
preload('imageCurriculumOn','images/nav_curriculum_on.gif');
preload('imageCurriculumOff','images/nav_curriculum_off.gif');
preload('imageFacilitiesOn','images/nav_facilities_on.gif');
preload('imageFacilitiesOff','images/nav_facilities_off.gif');
preload('imageProgramsOn','images/nav_programs_on.gif');
preload('imageProgramsOff','images/nav_programs_off.gif');
preload('imageCommunityOn','images/nav_community_on.gif');
preload('imageCommunityOff','images/nav_community_off.gif');
preload('imageCalendarOn','images/nav_calendar_on.gif');
preload('imageCalendarOff','images/nav_calendar_off.gif');
preload('imageGalleryOn','images/nav_gallery_on.gif');
preload('imageGalleryOff','images/nav_gallery_off.gif');
preload('imageContactOn','images/nav_contact_on.gif');
preload('imageContactOff','images/nav_contact_off.gif');