css
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  border: 4px solid #000;
}

body, html {
  font-family: "Arial", "Helvetica", sans-serif;
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  font-size: 16px;
  line-height: 1.5;
  color: #333;
  background-color: #fff;
  background-image: linear-gradient(90deg, #fff, #f0f0f0);
}

body::before {
  content: "";
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100px;
  background: linear-gradient(to top, #fff, #000);
  background-size: 100px;
  z-index: 1;
}

h1, h2, h3 {
  font-weight: bold;
  margin: 10px 0 10px 0;
  padding: 5px 0;
  border-bottom: 4px solid #000;
  text-align: center;
  color: #fff;
  background: linear-gradient(90deg, #000, #fff);
  background-size: 100px;
  background-position: 0 0;
  background-repeat: repeat-x;
}

h1 {
  font-size: 36px;
}

h2 {
  font-size: 24px;
}

h3 {
  font-size: 18px;
}

a {
  color: #f00;
  text-decoration: none;
  border: 2px solid #000;
  border-bottom: none;
  background: linear-gradient(90deg, #000, #f00);
  background-size: 100px;
  background-position: 0 0;
  background-repeat: repeat-x;
  display: inline-block;
  padding: 5px 10px;
}

a:hover {
  border-color: #f00;
  background-color: #000;
  color: #fff;
  text-decoration: none;
}

#main {
  width: 800px;
  margin: 0 auto;
  padding: 20px;
  background: linear-gradient(90deg, #f0f0f0, #fff);
  background-size: 100px;
  background-position: 0 0;
  background-repeat: repeat-x;
  box-shadow: 0 0 4px 0 #000;
}

#content {
  width: 100%;
  margin: 0;
  padding: 20px;
  background: linear-gradient(90deg, #000, #f00);
  background-size: 100px;
  background-position: 0 0;
  background-repeat: repeat-x;
  box-shadow: 0 0 4px 0 #000;
}

#footer {
  width: 100%;
  margin: 0;
  padding: 20px;
  background: linear-gradient(90deg, #000, #f00);
  background-size: 100px;
  background-position: 0 0;
  background-repeat: repeat-x;
  box-shadow: 0 0 4px 0 #000;
}

img {
  border: 4px solid #000;
  width: 100%;
  height: auto;
  margin: 10px 0 10px 0;
  background: linear-gradient(90deg, #000, #f00);
  background-size: 100px;
  background-position: 0 0;
  background-repeat: repeat-x;
}