Page 404 exemple 01 

<!DOCTYPE html>
<html lang="fr" prefix="og: http://ogp.me/ns#">
  <head>
    <title>Page 404 | par NGLESSON</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="author" content="Mezgani said">
    <meta name="copyright" content="NGLESSON">
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css">
    <link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet" type="text/css">
    <link href="style.css" rel="stylesheet" />
</head>
<body class="page-404">
    <div class="moon"></div>
    <div class="moon__crater moon__crater1"></div>
    <div class="moon__crater moon__crater2"></div>
    <div class="moon__crater moon__crater3"></div>
    <div class="star star1"></div>
    <div class="star star2"></div>
    <div class="star star3"></div>
    <div class="star star4"></div>
    <div class="star star5"></div>
    <div class="error">
      <div class="error__title">404</div>
      <div class="error__subtitle">Ooooops ...</div>
      <div class="error__description">La page que vous cherchez n'existe pas.</div>
      <br><br>
      <a href="https://www.mezganisaid.com/" class="error__button error__button--active">Page d'acceuil</a>
      <a href="javascript:history.back();" class="error__button">Retour à la page précédente</a>
    </div>
    <div class="astronaut">
      <div class="astronaut__backpack"></div>
      <div class="astronaut__body"></div>
      <div class="astronaut__body__chest"></div>
      <div class="astronaut__arm-left1"></div>
      <div class="astronaut__arm-left2"></div>
      <div class="astronaut__arm-right1"></div>
      <div class="astronaut__arm-right2"></div>
      <div class="astronaut__arm-thumb-left"></div>
      <div class="astronaut__arm-thumb-right"></div>
      <div class="astronaut__leg-left"></div>
      <div class="astronaut__leg-right"></div>
      <div class="astronaut__foot-left"></div>
      <div class="astronaut__foot-right"></div>
      <div class="astronaut__wrist-left"></div>
      <div class="astronaut__wrist-right"></div>
      <div class="astronaut__cord">
        <canvas id="cord" height="500px" width="500px"></canvas>
      </div>
      <div class="astronaut__head">
        <canvas id="visor" width="60px" height="60px"></canvas>
        <div class="astronaut__head-visor-flare1"></div>
        <div class="astronaut__head-visor-flare2"></div>
      </div>
    </div>
  <script src="script.js"></script>
</body>
</html>

html,
body {
  height: 100%;
  width: 100%;
  margin: 0px;
  background: linear-gradient(90deg, rgba(47,54,64,1) 23%, rgba(24,27,32,1) 100%);
}

.moon {
  background: linear-gradient(90deg, rgba(208,208,208,1) 48%, rgba(145,145,145,1) 100%);
  position: absolute;
  top: -100px;
  left: -300px;
  width: 900px;
  height: 900px;
  content: '';
  border-radius: 100%;
  box-shadow: 0px 0px 30px -4px rgba(0,0,0,0.5);
}

.moon__crater {
  position: absolute;
  content: '';
  border-radius: 100%;
  background: linear-gradient(90deg, rgba(122,122,122,1) 38%, rgba(195,195,195,1) 100%);
  opacity: 0.6;
}

.moon__crater1 {
  top: 250px;
  left: 500px;
  width: 60px;
  height: 180px;
}

.moon__crater2 {
  top: 650px;
  left: 340px;
  width: 40px;
  height: 80px;
  transform: rotate(55deg);
}

.moon__crater3 {
  top: -20px;
  left: 40px;
  width: 65px;
  height: 120px;
  transform: rotate(250deg);
}

.star {
  background: grey;
  position: absolute;
  width: 5px;
  height: 5px;
  content: '';
  border-radius: 100%;
  transform: rotate(250deg);
  opacity: 0.4;
  animation-name: shimmer;
  animation-duration: 1.5s;
  animation-iteration-count: infinite;
  animation-direction: alternate;
}

@keyframes shimmer {
  from {opacity: 0;}
  to {opacity: 0.7;}
}

.star1 {
  top: 40%;
  left: 50%;
  animation-delay: 1s;
}

.star2 {
  top: 60%;
  left: 90%;
  animation-delay: 3s;
}

.star3 {
  top: 10%;
  left: 70%;
  animation-delay: 2s;
}

.star4 {
  top: 90%;
  left: 40%;
}

.star5 {
  top: 20%;
  left: 30%;
  animation-delay: 0.5s;
}

.error {
  position: absolute;
  left: 100px;
  top: 400px;
  transform: translateY(-60%);
  font-family: 'Righteous', cursive;
  color: #363e49;
}

.error__title {
  font-size: 10em;
}

.error__subtitle {
  font-size: 2em;
}

.error__description {
  opacity: 0.5;
}

.error__button {
  min-width: 7em;
  margin-top: 3em;
  margin-right: 0.5em;
  padding: 0.5em 2em;
  outline: none;
  border: 2px solid #2f3640;
  background-color: transparent;
  border-radius: 8em;
  color: #576375;
  cursor: pointer;
  transition-duration: 0.2s;
  font-size: 0.75em;
  font-family: 'Righteous', cursive;
}

.error__button:hover {
  color: #21252c;
}

.error__button--active {
  background-color: #9B56B4;
  border: 2px solid #9B56B4;
  color: white;
}

.error__button--active:hover {
  box-shadow: 0px 0px 8px 0px rgba(0,0,0,0.5);
  color: white;
}

.astronaut {
  position: absolute;
  width: 185px;
  height: 300px;
  left: 70%;
  top: 50%;
  transform: translate(-50%, -50%) rotate(20deg) scale(1.2);
}

.astronaut__head {
  background-color: white;
  position: absolute;
  top: 60px;
  left: 60px;
  width: 60px;
  height: 60px;
  content: '';
  border-radius: 2em;
}

.astronaut__head-visor-flare1 {
  background-color: #7f8fa6;
  position: absolute;
  top: 28px;
  left: 40px;
  width: 10px;
  height: 10px;
  content: '';
  border-radius: 2em;
  opacity: 0.5;
}

.astronaut__head-visor-flare2 {
  background-color: #718093;
  position: absolute;
  top: 40px;
  left: 38px;
  width: 5px;
  height: 5px;
  content: '';
  border-radius: 2em;
  opacity: 0.3;
}

.astronaut__backpack {
  background-color: #bfbfbf;
  position: absolute;
  top: 90px;
  left: 47px;
  width: 86px;
  height: 90px;
  content: '';
  border-radius: 8px;
}

.astronaut__body {
  background-color: #e6e6e6;
  position: absolute;
  top: 115px;
  left: 55px;
  width: 70px;
  height: 80px;
  content: '';
  border-radius: 8px;
}

.astronaut__body__chest {
  background-color: #d9d9d9;
  position: absolute;
  top: 140px;
  left: 68px;
  width: 45px;
  height: 25px;
  content: '';
  border-radius: 6px;
}

.astronaut__arm-left1 {
  background-color: #e6e6e6;
  position: absolute;
  top: 127px;
  left: 9px;
  width: 65px;
  height: 20px;
  content: '';
  border-radius: 8px;
  transform: rotate(-30deg);
}

.astronaut__arm-left2 {
  background-color: #e6e6e6;
  position: absolute;
  top: 102px;
  left: 7px;
  width: 20px;
  height: 45px;
  content: '';
  border-radius: 8px;
  transform: rotate(-12deg);
  border-top-left-radius: 8em;
  border-top-right-radius: 8em;
}

.astronaut__arm-right1 {
  background-color: #e6e6e6;
  position: absolute;
  top: 113px;
  left: 100px;
  width: 65px;
  height: 20px;
  content: '';
  border-radius: 8px;
  transform: rotate(-10deg);
}

.astronaut__arm-right2 {
  background-color: #e6e6e6;
  position: absolute;
  top: 78px;
  left: 141px;
  width: 20px;
  height: 45px;
  content: '';
  border-radius: 8px;
  transform: rotate(-10deg);
  border-top-left-radius: 8em;
  border-top-right-radius: 8em;
}

.astronaut__arm-thumb-left {
  background-color: #e6e6e6;
  position: absolute;
  top: 110px;
  left: 21px;
  width: 10px;
  height: 6px;
  content: '';
  border-radius: 8em;
  transform: rotate(-35deg);
}

.astronaut__arm-thumb-right {
  background-color: #e6e6e6;
  position: absolute;
  top: 90px;
  left: 133px;
  width: 10px;
  height: 6px;
  content: '';
  border-radius: 8em;
  transform: rotate(20deg);
}

.astronaut__wrist-left {
  background-color: #9B56B4;
  position: absolute;
  top: 122px;
  left: 6.5px;
  width: 21px;
  height: 4px;
  content: '';
  border-radius: 8em;
  transform: rotate(-15deg);
}

.astronaut__wrist-right {
  background-color: #9B56B4;
  position: absolute;
  top: 98px;
  left: 141px;
  width: 21px;
  height: 4px;
  content: '';
  border-radius: 8em;
  transform: rotate(-10deg);
}

.astronaut__leg-left {
  background-color: #e6e6e6;
  position: absolute;
  top: 188px;
  left: 50px;
  width: 23px;
  height: 75px;
  content: '';
  transform: rotate(10deg);
}

.astronaut__leg-right {
  background-color: #e6e6e6;
  position: absolute;
  top: 188px;
  left: 108px;
  width: 23px;
  height: 75px;
  content: '';
  transform: rotate(-10deg);
}

.astronaut__foot-left {
  background-color: white;
  position: absolute;
  top: 240px;
  left: 43px;
  width: 28px;
  height: 20px;
  content: '';
  transform: rotate(10deg);
  border-radius: 3px;
  border-top-left-radius: 8em;
  border-top-right-radius: 8em;
  border-bottom: 4px solid #9B56B4;
}

.astronaut__foot-right {
  background-color: white;
  position: absolute;
  top: 240px;
  left: 111px;
  width: 28px;
  height: 20px;
  content: '';
  transform: rotate(-10deg);
  border-radius: 3px;
  border-top-left-radius: 8em;
  border-top-right-radius: 8em;
  border-bottom: 4px solid #9B56B4;
}

a{
    text-decoration: none;
    font-weight: bold !important;
}
function drawVisor() {
    const canvas = document.getElementById('visor');
    const ctx = canvas.getContext('2d');
    
    ctx.beginPath();
    ctx.moveTo(5, 45);
    ctx.bezierCurveTo(15, 64, 45, 64, 55, 45);
    
    ctx.lineTo(55, 20);
    ctx.bezierCurveTo(55, 15, 50, 10, 45, 10);
    
    ctx.lineTo(15, 10);
    
    ctx.bezierCurveTo(15, 10, 5, 10, 5, 20);
    ctx.lineTo(5, 45);
    
    ctx.fillStyle = '#2f3640';
    ctx.strokeStyle = '#f5f6fa';
    ctx.fill();
    ctx.stroke();
  }
  
  const cordCanvas = document.getElementById('cord');
  const ctx = cordCanvas.getContext('2d');
  
  let y1 = 160;
  let y2 = 100;
  let y3 = 100;
  
  let y1Forward = true;
  let y2Forward = false;
  let y3Forward = true;
  
  function animate() {
    requestAnimationFrame(animate);
    ctx.clearRect(0, 0, innerWidth, innerHeight);
    
    ctx.beginPath();
    ctx.moveTo(130, 170);
    ctx.bezierCurveTo(250, y1, 345, y2, 400, y3);
    
    ctx.strokeStyle = 'white';
    ctx.lineWidth = 8;
    ctx.stroke();
   
    
    if (y1 === 100) {
      y1Forward = true;
    }
    
    if (y1 === 300) {
      y1Forward = false;
    }
    
    if (y2 === 100) {
      y2Forward = true;
    }
    
    if (y2 === 310) {
      y2Forward = false;
    }
    
    if (y3 === 100) {
      y3Forward = true;
    }
    
    if (y3 === 317) {
      y3Forward = false;
    }
    
    y1Forward ? y1 += 1 : y1 -= 1;
    y2Forward ? y2 += 1 : y2 -= 1;
    y3Forward ? y3 += 1 : y3 -= 1;
  }
  
  drawVisor();
  animate();
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