gecko-dev/browser/themes/shared/aboutSocialError.css

@import url("chrome://global/skin/in-content/common.css");

#errorPageContainer {
  min-width: 50%;
}

#errorTitle {
  background: url("chrome://global/skin/icons/info.svg") left 0 no-repeat;
  background-size: 2em;
  -moz-padding-start: 3em;
}

#button-box {
  text-align: center;
  width: 75%;
  margin: 0 auto;
}

button {
  width: auto !important;
  min-width: 150px;
}

@media all and (max-width: 300px) {
  body {
    padding: 0px 10px;
  }
  #errorPageContainer {
    min-width: 100%;
  }
  #errorTitle {
    background: none;
    -moz-padding-start: 0 !important;
  }
  button {
    width: auto !important;
    min-width: auto !important;
  }
}