var ExternalLinks = new Class({	
	options: {
		selector: 'a[rel="external"]',
		warning: ' (opens in a new window)'
	},

	initialize: function(options) {
	    this.setOptions(options);
	    
	    $$(this.options.selector).each(
	        function (el) {
	        	el.title = el.title + this.options.warning;
	        
			el.addEvent('click', 
				function (e) {
					window.open(el.href);
					
					return false;
				}
			);
	        }.bind(this)
	    );
	}
});

ExternalLinks.implement(new Events, new Options);