JSFiddle - React, Tailwind, and code Playground

HTML

<div class="bg">
        <img
          id="plain"
          src="https://cdn.glitch.com/a65b2bac-6bb8-4ddd-a2b6-a4fb23492184%2F416-4161308_window-transparent-background-window.png?v=1601816253247"
        />

        <img
          id="gif"
          src="https://cdn.glitch.com/a65b2bac-6bb8-4ddd-a2b6-a4fb23492184%2Fgiffram.gif?v=1601804252711"
        />
      </div>
      
      
        <a id="next" href="90.html"> NEXT PAGE  </a>

CSS

.bg {
  z-index: -100;
  padding: 0;
  top: 0;
}

.bg img {
  z-index: -10;
  min-height: 100%;

  width: 100%;
  height: 100%;

  position: fixed;
  top: 0;
  left: 0;
}

#gif {
  z-index: -15;
}


#next {

text-decoration: none;
display: inline-block;
position: fixed;
width: 25vw;
height: 7vh;
margin: 0;
text-align: center;
bottom: 10vh;
right: 0;
margin-right: 2%;
z-index: 50;
background-color: red;
font-size: 3vw;
color: black;



}