webextensions-examples/proxy-blocker/options/options.css

body {
  width: 25em;
  font-family: "Open Sans Light", sans-serif;
  font-size: 0.9em;
  font-weight: 300;
}

.title, #blocked-hosts {
  margin: 1em;
}

.title {
  font-size: 1.2em;
}