function preloadMoreImages() {
if (document.images)
	{
	var btn_sitecredits_roll = new Image
		btn_sitecredits_roll.src = "images/btn_sitecredits_over.gif"
	var btn_introduction_roll = new Image
		btn_introduction_roll.src = "images/btn_introduction_over.gif"
	var btn_scientific_roll = new Image
		btn_scientific_roll.src = "images/btn_scientific_over.gif"
	var btn_literature_roll = new Image
		btn_literature_roll.src = "images/btn_literature_over.gif"
	var btn_oldnewspapers_roll = new Image
		btn_oldnewspapers_roll.src = "images/btn_oldnewspapers_over.gif"
	var btn_archethics_roll = new Image
		btn_archethics_roll.src = "images/btn_archethics_over.gif"
	var btn_sharing_roll = new Image
		btn_sharing_roll.src = "images/btn_sharing_over.gif"
	var btn_earlymaps_roll = new Image
		btn_earlymaps_roll.src = "images/btn_earlymaps_over.gif"
	}
}