var ImageRollover = Behavior.create({
	orig_name: null,
	image_ext: null,
	roll_suffix: null,

	initialize: function(roll_suffix) {
		this.roll_suffix = roll_suffix
		matches = this.element.src.match(/(.*)((?:.gif|.jpg|.png).*)/);
		this.orig_name = matches[1]; 
		this.image_ext = matches[2];
	},

	onmouseover: function() {
		this.element.src = this.orig_name + this.roll_suffix + this.image_ext;
	},

	onmouseout: function() {
		this.element.src = this.orig_name + this.image_ext;
	}
});

Event.addBehavior({
	'#global-menu a img': ImageRollover('_over')
});