media_queries.css

main {
  display: block;
  width: 1000px;
  height: 50px;
  margin: 0 auto;
  background-color: red;
}

@media (max-width: 980px) {
  main {
    width: 700px;
  }
}

@media (max-width: 480px) {
  main {
    width: 100px;
  }
}