header{
  background: red;
}
footer{
  background: blue;
}
.content{
  margin-bottom: auto;
  background: yellow;
}
body,html {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 0;
  margin: 0;
}
.wrapper{
  display: flex;
  flex-direction: column;
  flex: 1;
}