function MakeImageArray(n) {
	this.length = n;
	for (var i = 1; i<=n; i++) {
	  this[i] = new Image();
	}
	return this;
}

function isOpera() {
	// return true if browser identifies as Opera
	return (window.opera)?true:false;
}

// note, not supported by Opera - browser scrolls to top of page on change of image
// (browser detect only works on Operas which id themselves as Opera)

function on(num) {
	if (document.images && !isOpera()){
		if (imageon[num].src != "") {
			document["display_map"].src=imageon[num].src;
		}
	}
}

function off() {
	if (document.images && !isOpera()){
		if (imageoff[1].src != "") {
			document["display_map"].src=imageoff[1].src;
		}
	}
}