.container {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
  border-bottom: 3px solid #FFB700;
  padding: 1rem .75rem 1rem;
}

.header {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
}

.header h1, .header a {
  font-size: 3rem;
  font-weight: normal;
  margin-bottom: .5rem;
  text-decoration: none;
}

.header p {
  font-size: 1rem;
  font-weight: normal;
  margin-bottom: 1rem;
}

.nav ul {
  padding: 0;
  margin: 0;
}

.nav li {
  display: inline;
  list-style: none;
  padding: 0 1rem 0 0;
}

@media screen and (min-width: 470px) {
  .container {
    align-items: center;
    padding: 1.5rem 2rem 1rem;
  }
  .header {
    align-items: center;
  }
  .nav li {
    padding: 0 1rem;
  }
}

.container {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
  border-bottom: 3px solid #FFB700;
  padding: 1rem .75rem 1rem;
}

.header {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  justify-content: center;
}

.header h1, .header a {
  font-size: 3rem;
  font-weight: normal;
  margin-bottom: .5rem;
  text-decoration: none;
}

.header p {
  font-size: 1rem;
  font-weight: normal;
  margin-bottom: 1rem;
}

.nav ul {
  padding: 0;
  margin: 0;
}

.nav li {
  display: inline;
  list-style: none;
  padding: 0 1rem 0 0;
}

.nav a {
  text-decoration: none;
  border-bottom: 1px solid #4D4D4D;
}

@media screen and (min-width: 470px) {
  .container {
    align-items: center;
    padding: 1.5rem 2rem 1rem;
  }
  .header {
    align-items: center;
  }
  .nav li {
    padding: 0 1rem;
  }
}

Fix navigation link underline style
Fix navigation link underline style
