404.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>Page Not Found</title>
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="icon" href="favicon.ico" />
    <style>
      * {
        line-height: 1.2;
        margin: 0;
      }

      html {
        color: #888;
        display: table;
        font-family: sans-serif;
        height: 100%;
        text-align: center;
        width: 100%;
      }

      body {
        display: table-cell;
        vertical-align: middle;
        margin: 2em auto;
      }

      h1 {
        color: #555;
        font-size: 2em;
        font-weight: 400;
      }

      p {
        margin: 0 auto;
        width: 280px;
      }

      @media only screen and (max-width: 280px) {
        body,
        p {
          width: 95%;
        }

        h1 {
          font-size: 1.5em;
          margin: 0 0 0.3em;
        }
      }
    </style>
  </head>
  <body>
    <h1>Page Not Found</h1>
    <p>Sorry, but the page you were trying to view does not exist.</p>
  </body>
</html>
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