body
{
    background: #eee;
}
div#main
{
    color: #000; background: #fff;
    margin-left: auto;
    margin-right: auto;
    border: 1px solid #000;
    padding: 1em;
    width: 50em;
}
.center
{
    text-align: center;
}
pre
{
    background: #eef;
    margin-left: 3em;
    margin-right: 3em;
    padding: 1em;
}
table
{
    color: #000; background: #fee;
    margin-left: auto;
    margin-right: auto;
    border-collapse: collapse;
}
caption
{
    margin-left: auto;
    margin-right: auto;
    caption-side: bottom;
}
th
{
    border-bottom: 1px solid #000;
    text-align: center;
    font-weight: bold;
}