/usr/share/epiphany-browser/pages/error.css is in epiphany-browser-data 3.18.5-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | /* Global CSS for error pages */
h1 {
        color: #babdb6;
        text-shadow: 0 1px 0 white;
        margin-bottom: 0;
}
html {
        font-family: Cantarell, sans-serif;
        font: 11pt cantarell;
        color: #2e3436;
        padding: 20px 20px 0 20px;
        background-color: #f6f6f4;
        background-image: -webkit-gradient(
                linear,
                left top,
                left bottom,
                color-stop(0, #eeeeec),
                color-stop(1, #f6f6f4)
        );
        background-size: 100% 5em;
        background-repeat: no-repeat;
}
#container {
    padding: 2em;
    margin: 2em auto;
    background-color: #fff;
    border-radius: 1em;
    border: 2px solid #d3d7cf;
    max-width: 650px;
}
#content {
    vertical-align: top;
}
#content h1 {
    margin-top: 0;
}
#content .buttonbox {
    text-align: right;
}
html[dir="rtl"] #content .buttonbox {
    text-align: left;
}
 |