a {color:#3498db;text-decoration:none;}
a:hover{color:#2980b9; text-decoration:underline;}
body {
    background-color:#fff;
    margin: 20px 15%;
    font-family: "Lucida Grande", "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-size:18px;
    line-height: 1.72222;
    color: rgb(52, 73, 94);
}
h1, h2,h3,h4 {font-weight: 700; color:#34495e;}
h1{font-size:42px;}
h2{font-size:32px;}
h3{font-size:20px;}
pre,code {font-family: Monaco, Menlo, Consolas, "Courier New", monospace; color:#6f7c7d;}
.back{
    display:block;
    text-align:center;
    font-size:120%;
    margin:40px auto;
}