* {
  border: 1px solid;
  background: lightcyan;
}
*:nth-child(odd) {
  background: khaki;
}
*:only-child {
  background: palegreen;
}

body {
  margin: 0;
}

#header, #main, #footer, #menu, #links, #socials {
  display: flex;
}

ul {
  list-style: none;
}