.git-link {
    z-index: 100;
    position: fixed;
    top: 0;
    right: 0;
    border: 0;
    height: 149px;
    width: 149px;
    background-image: url(//images.cnblogs.com/cnblogs_com/pppikaqiu/1296571/o_github%E4%BC%A0%E9%80%81%E9%97%A8.png);
}

.git-link:hover {
    z-index: 100;
    position: fixed;
    top: 0;
    right: 0;
    border: 0;
    height: 149px;
    width: 149px;
    background-image: url(//images.cnblogs.com/cnblogs_com/pppikaqiu/1296571/o_github%E4%BC%A0%E9%80%81%E9%97%A8.png);
}