window.addEvent('domready', function(){
    if($$('.thumb-image') != null){
        $$('.thumb-image').each(function(link){
		    link.addEvent('click', function(event) {
			    event.preventDefault();
			    var thumb_image = link.get('href');
				var big_image = $('big_image');
			    big_image.set('src',thumb_image);
	        });
	    });
	}
});