.wrapper {
    width: 960px;
    margin: auto;
}
main {
    float: left;
    width: 640px;
}
main ol li {
    list-style-type: decimal-leading-zero;
}
aside {
    float: right;
    width: 320px;
}
footer {
    clear: both;
}
a:hover {
    color:aqua;
}
a:visited {
    color:gold;
}
.intro {
    border: 2px solid red;
    border-radius: 25px;
    background-color: coral;
    box-shadow: 5px 10px #888888;
}