cookie.set('skin', 'blue', 365, '') // 问题就在这里最后的''

var Cookie = {
    isAllowed: document.cookie && document.cookie != '',
    set: function(cn, cv, d, dm){
        var now = new Date();
        var expire = new Date();
        if (d == null || d == 0) {
            d = 1;
        }
        expire.setTime(now.getTime() + 3600000 * 24 * d);
        document.cookie = cn + '=' + encodeURI(cv) + ';expires=' + expire.toGMTString() + ';domain=' + dm + '; path=/';
    },
    clear: function(cn, dm){
        if (this.get(name)) {
            document.cookie = cn + '=' + ((domain) ? '; domain=' + dm : '') + '; expires=Thu, 01-Jan-70 00:00:01 GMT';
        }
    },
    get: function(cn){
        var dc = document.cookie;
        var prefix = cn + '=';
        var begin = dc.indexOf('; ' + prefix);
        
        if (begin == -1) {
            begin = dc.indexOf(prefix);
            if (begin != 0) {
                return null;
            }
        }
        else {
            begin += 2;
        }
        
        var end = document.cookie.indexOf(';', begin);
        if (end == -1) {
            end = dc.length;
        }
        return decodeURI(dc.substring(begin + prefix.length, end));
    }
};

function Opacity(element, value){
    var style = element.style;
    style.opacity = value / 100;
    style.filter = "alpha(opacity=" + value + ")";
}