html {
    /* background-color: #ccc; */
    background-image: url("background.gif");
}

table.content td {
    padding: 4px
}

pre {
    overflow-x: auto;
}

article img {
    max-width: 100%;
}

.center {
    margin-left: auto; 
    margin-right: auto;
}

.text_center {
    text-align: center;
}

td.active {
    background-color: #ffffff80;
}

article table, article th, article td {
    border: 1px solid black;
    border-style: solid;
    border-collapse: collapse;
}

div.page {
    display: block;
    width: 612px;
}

div.footer {
    display: block;
    width: 620px;
}


h1 {
    font-size: 25px;
}

h2 {
    font-size: 22px;
}

h3 {
    font-size: 19px;
}

h4 {
    font-size: 17px;
}

h5 {
    font-size: 15px;
}

h6 {
    font-size: 13px;
}