var HoverBehavior = Class.create();
HoverBehavior.prototype = {
    initialize: function() {
        // with each argument
        $A(arguments).each( function(arg) {
            // iterate over all divs
            $$('div').each( function(tag) {
                // with class matching the given argument
                if ( tag.className == arg) {
                    // add mouseover & mouseout methods
                    Event.observe(tag, 'mouseover', function() { Element.addClassName(tag, 'hover'); });
                    Event.observe(tag, 'mouseout', function() { Element.removeClassName(tag, 'hover'); });
                }
            });
        });
    }
};