.ad-300x250 {
    width: 300px;
    height: 250px;
    margin: 10px auto;
}
.ad-728x90 {
    width: 728px;
    height: 90px;
    margin: 10px auto;
}
.adsense-970-90-text {
    width: 970px;
    height: 90px;
    margin: 10px auto;
    padding: 10px;
    background-color: #fff;
}
.m-0 {
    margin: 0;
}
a {
    color: #00f;
    text-decoration: none;
}
    a:hover {
        text-decoration: underline;
    }
body {
    font-family: Arial, sans-serif;
    font-size: 1em;
    line-height: 1.6em;
    margin: 0px;
    background-color: #eee;
    overflow-wrap: break-word;
}
code {
    display: block;
    padding: 10px;
    border: 1px dashed #000;
    white-space: pre-wrap;
}
div.panel {
    background-color: #fff;
    padding: 10px;
    margin-bottom: 10px;
}
footer {
    background-color: #fff;
    margin: 10px auto 0;
    padding: 10px;
}
h1 {
    font-size: 2em;
    margin: 0;
}
h2 {
    margin: 0 0 16px 0;
    font-size: 1.5em;
}
h3 {
    margin: 0 0 16px 0;
    font-size: 1.25em;
}
h4 {
    font-size: 1em;
}
header {
    background-color: #fff;
    margin: 0 auto 10px;
    padding: 10px;
}
hr {
    border: 0;
    height: 1px;
    color: #ddd;
    background-color: #ddd;
}
iframe.website {
    display: block;
    width: 100%;
    border: 0;
}
input, textarea {
    background-color: #fff;
    border: 1px solid #ddd;
    outline: none;
    padding: 10px;
    font-size: 20px;
    font-family: sans-serif;
}
    input[type=submit] {
        border-radius: 5px;
        background-color: #eee;
        padding: 10px;
    }
    input[type=submit]:active {
        background-color: #eee;
    }

main {
    display: flex;
    align-items: flex-start;
    width: 100%;
    max-width: 990px;
    margin: 0 auto 10px;
}
    main > div :last-child {
        margin-bottom: 0;
    }
    main .left {
        background-color: #fff;
        width: 200px;
        margin-right: 10px;
        padding: 10px;
    }
        main .left ol {
            margin: 0px;
            padding: 0px;
            list-style-type: none;
        }
            main .left ol li+li {
                margin-top: 1em;
            }
            main .left ol ol {
                list-style-type: disc;
                padding-left: 20px;
            }
                main .left ol ol li {
                    margin: 0;
                }
    main .right {
        width: 760px;
    }
ol.panels {
    list-style-type: none;
    margin: 0;
    padding: 0;
}
    ol.panels li {
        background-color: #fff;
        padding: 10px;
        margin-bottom: 10px;
    }
    ol.panels li p:first-child {
        margin-top: 0;
    }
pre {
    white-space: pre;           /* CSS 2.0 */
    white-space: pre-wrap;      /* CSS 2.1 */
    white-space: pre-line;      /* CSS 3.0 */
    white-space: -pre-wrap;     /* Opera 4-6 */
    white-space: -o-pre-wrap;   /* Opera 7 */
    white-space: -moz-pre-wrap; /* Mozilla */
    white-space: -hp-pre-wrap;  /* HP Printers */
    word-wrap: break-word;      /* IE 5+ */
    padding: 10px;
    border: 1px dashed #000;
}
textarea {
    resize: vertical;
    width: 600px;
    height: 200px;
}

@media screen and (min-width: 1010px) {
    div.columns {
        display: flex;
    }
    footer .container {
        width: 990px;
        margin: 0 auto;
        display: flex;
        justify-content: space-between;
    }
    header .container {
        width: 990px;
        margin: 0 auto;
    }
        header .container div.column {
            width: 50%;
        }
        header .container div.column:nth-child(2) {
            text-align: right;
            align-self: end;
        }
    iframe.website {
        height: 400px;
    }
}
@media screen and (max-width: 1009.9px) {
    header .container div.column:first-child {
        margin-bottom: 1em;
    }
    iframe.website {
        height: 200px;
    }
    main {
        flex-direction: column-reverse;
    }
    main .left {
        background-color: #fff;
        width: 100%;
        margin-top: 10px;
        padding: 10px;
        box-sizing: border-box;
    }
    main .right {
        width: 100%;
    }
}