<!-- hide from old browsersvar imgID = new Array('about','exhib','rsrch','store');var navImgOn = new Array();var navImgOff = new Array();function cacheImages(){	for(i=0;i<imgID.length;i++){		var nam = imgID[i];		navImgOn[nam] = new Image;		navImgOn[nam].src = "images/main_menu/main_"+nam+"_on.gif";		navImgOn[nam].useMap = "#main_menu_"+nam;		navImgOff[nam] = new Image;		navImgOff[nam].src = "images/main_menu/main_"+nam+".gif";	}}function rollOn(nam){	document.images[nam].src=navImgOn[nam].src;	document.images[nam].useMap=navImgOn[nam].useMap;	return true;}function rollOff(nam){	document.images[nam].src=navImgOff[nam].src;	return true;}//-->