function preloadImages() {
	var artbyculture = new Image
		artbyculture.src = "images/byculture-over.jpg"
	var artbytheme = new Image
		artbytheme.src = "images/bytheme-over.jpg"
	var comparecontrast = new Image
		comparecontrast.src = "images/comparecontrast-over.jpg"
	var viewallart = new Image
		viewallart.src = "images/viewart-over.jpg"
}

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