zammad/public/assets/error/style.css

@font-face {
  font-family: 'Fira Sans';
  src: url('firasans-regular-webfont.eot');
  src: url('firasans-regular-webfont.eot?#iefix') format('embedded-opentype'),
       url('firasans-regular-webfont.woff') format('woff'),
       url('firasans-regular-webfont.ttf') format('truetype');
  font-weight: normal;
  font-style: normal;
}

html {
  font-family: "Fira Sans";
  height: 100%;
  color: #8c959c;
  background: #f8f9fa;
  text-align: center;
}

.dark {
  background: #444a4f;
  color: #919497;
}

body {
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-flex-direction: column;
  -ms-flex-direction: column;
  flex-direction: column;
  -webkit-justify-content: center;
  -ms-flex-pack: center;
  justify-content: center;
  -webkit-align-items: center;
  -ms-flex-align: center;
  align-items: center;
  height: 100%;
  min-height: 600px;
  margin: 0;
  padding: 40px 10px;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  overflow-x: hidden;
}

body.error-message {
  height: auto;
}

pre {
  text-align: left;
  padding-bottom: 1em;
  background: white;
  color: #222;
}

h1 {
  margin: 0;
  color: #444a4f;
}

.dark h1 {
  color: white;
}

a {
  color: #f1d158;
  text-decoration: none;
}
a:visited {
  color: #ccb250;
}

ul {
  text-align: left;
}

p {
  max-width: 400px;
  margin: 0 0 20px;
}

.error-image {
  height: 650px;
  width: 100%;
  margin: 30px 0;
  background-size: contain;
  background-position: center;
  background-repeat: no-repeat;
}