浏览器默认的滚动条样式不好看，用以下CSS可将滚动条样式优化为自己想要的效果

::-webkit-scrollbar-track-piece {
    background-color: #fff;
    -webkit-border-radius: 0
}
::-webkit-scrollbar {
    width: 10px;
    height: 10px
}
::-webkit-scrollbar-thumb {
    height: 50px;
    background-color: #b8b8b8;
    -webkit-border-radius: 6px;
    outline: 2px solid #fff;
    outline-offset: -2px;
    border: 2px solid #fff;
    filter: alpha(opacity = 50);
    -moz-opacity: 0.5;
    -khtml-opacity: 0.5;
    opacity: 0.5
}
::-webkit-scrollbar-thumb:hover {
    height: 50px;
    background-color: #878987;
    -webkit-border-radius: 6px
}