metamask-extension/ui/app/css/itcss/components/header.scss

.app-header {
  align-items: center;
  visibility: visible;
  background: $gallery;
  height: 14.4vh;
  max-height: 97px;
  position: relative;
  z-index: $header-z-index;
  display: flex;
  flex-flow: column nowrap;

  @media screen and (max-width: 575px) {
    position: fixed;
    height: 34px;
    width: 100%;
    box-shadow: 0 2px 2px 1px rgba(0, 0, 0, .08);
    z-index: $mobile-header-z-index;
  }
}

.app-header-contents {
  display: flex;
  justify-content: space-between;
  flex-flow: row nowrap;
  width: 100%;
  height: 6.9vh;

  @media screen and (min-width: 576px) {
    width: 85vw;
  }

  @media screen and (min-width: 769px) {
    width: 80vw;
    height: 6.9vh;
  }

  @media screen and (min-width: 1281px) {
    width: 65vw;
  }
}

.app-header h1 {
  font-family: 'Montserrat Regular';
  text-transform: uppercase;
  color: #22232c; // $shark
}

h2.page-subtitle {
  font-family: 'Montserrat Regular';
  text-transform: uppercase;
  color: #aeaeae;
  font-size: 1em;
  margin: 12px;
}

.network-component-wrapper {
  display: flex;
  flex-direction: row;
  align-items: center;
}

.left-menu-wrapper {
  display: flex;
  flex-direction: row;
  align-items: center;
}