jQuery.fn.rollover = function(){
    // alert(this.length);
    this.each(function(i, el) {
        if ($(el).attr('src') != undefined)
        {
            // rollover namespace (append to filename)
            var ro = '-ro';
            // element source attr
            var src = $(el).attr('src');
            // source item extension
            var ext = src.split(".").pop();
            // rollover item source
            var rol = src.substr(0, src.length - ext.length - 1) + ro + '.' + ext;
            // preloading
            var newItem = $(el).clone();
            newItem.attr('src', rol);
            // replace element on mouse enter
            $(el).hover(function(){
                $(this).attr('src', rol);
            }, function(){
                $(this).attr('src', src)
            });
        }
        else
        {
            throw('Rollover only works on elements with a src attribute.');
        }
    })
}