custom.css

#notebook_panel { /* main background */
    background: #AAA;
    color: #f6f6f6;
}

div #notebook { /* centre the content */
    background: #fff;
    color: #333;
    width: 130ex;
    margin: auto;
    padding-left: 0em;
    padding-right: 1em;
    padding-top: 2ex;
}
/* remove big margins around title */
div.text_cell_render.border-box-sizing.rendered_html {
    margin: 0;
    padding: 1; 
    margin-left: 1ex;
}
div.cell.text_cell.border-box-sizing {
    margin: 0;
    padding: 0; 
}
.rendered_html h1 {
    margin: 0;
    padding: 0;
}
.rendered_html h2 {
    margin: 0;
    padding: 0;
}
.rendered_html h3 {
    margin: 0;
    padding: 0;
}

div.cell { /* set cell width to about 80 chars */
    width: 55em;
}

div.cell.code_cell { /* area that contains code + output */
    background: #fff;
    border: none;
    border-radius: 10px;
    padding-top: 1ex;
}
/* header colours and fonts */
h1 { color: #2F6E99;font-family:"Comic Sans MS", cursive, sans-serif }
h2 { color: #CC4D49; font-family:"Georgia", cursive, sans-serif}
h3 { color: #549ACC; font-style: italic; font-weight: normal}