style.css

header {
  display:block;
  text-align: center;
  height:55px;
   background-image: linear-gradient(to right, pink, purple);
  border:5px solid black;
  color:black;
}
.square {
  border:5px solid black;
  display:block;
  position:absolute;
  left:35%;
  top:10%;
   background-image: linear-gradient(to right, pink, purple);
  width: 30%;
  height: 20px;
  margin:20px
}
#subtitle {
  text-align:center;
}
.content {
  background-image: linear-gradient(to right, pink, purple);
  border:5px double black;
  display:inline-block;
  position: absolute;
  bottom:85px;
  left:30%;
  top:15%;
  text-align: left;
  font-size: 20px;
  font-size: 1vw;
  width: 40%;
  margin:20px;
  padding:5px;
  height: fit-content;
}
.content p{
  font-size: 25px;
}
.sidebar {
   background-image: linear-gradient(to right, pink, purple);
  border:5px solid black;
  padding:3px;
  display:inline-block;
  position: absolute;
  right:5%;
  top: 20%;
  bottom:85px;
width:246px;
height:400px;
}
h4 {
  font-size: 20px;
}
body {
  height:fit-content;
}
footer {
  display:inline-block;
  position: fixed;
  width:100%;
  bottom:0;
  height:40px;
  background-image: linear-gradient(to right, pink, purple);
  border: 5px solid black;
}
.blended {
  background-image:url(https://qph.fs.quoracdn.net/main-qimg-7f4ff01964a4d5065f3fc28fdbbb6057-c);
  background-repeat: repeat-x;
  background-color: aqua;
  background-blend-mode:multiply;
height:100%;
}