body {
   
    margin-left: auto;
    margin-right: auto;
    width: 750px;
}

header {
    text-align: center;
}

nav {
    width: 750px;
}

img {
    width: 100%;
    text-align: center;
}

main p {
    text-align: center;
    font-size: 20px;
}

footer {
  height: 40px;
  width: 750px;
  font-size: 12px;
  padding-left: 10px;
  padding-right: 10px;
  background-color: green;
}