html,
body {
  font-family: Arial, Helvetica, sans-serif;
  margin: 0;
  padding: 0;
}
body {
  min-width: 340px;
  overflow: scroll;
}
main {
  width: 80%;
  margin: 0 auto;
}

header,
footer {
  padding: 0 10%;
}

@media screen and (max-width: 800px) {
  main {
    width: 100%;
  }
  header,
  footer {
    padding: 0 0;
  }
}