.main
{
    width:800px;
    display: block;
    margin-left: auto;
    margin-right: auto;
    text-align:center;
}

.top{
    display: block;
    margin-left: auto;
    margin-right: auto;
    text-align:center;
}

.middle{
    display: block;
    margin-left: auto;
    margin-right: auto;
    text-align:center;
}