<div class="box">
        <a class="button" href="#">Let me Pop up</a>
    </div> 

    <div id="popup1" class="overlay">
      <div class="popup" >
        <h2>Quite simple</h2>
        <a class="close" href="#popup1">×</a>
        <div class="content">
          Lorem ipsum dolor sit amet, consectetuer adipiscing elit, seding nonummy nibh euismod.
        </div>
      </div>
    </div>
 .box {
            width: 20%;
            margin: 0 auto;
            background: rgba(255, 255, 255, 0.2);
            padding: 35px;
            border: 2px solid #fff;
            border-radius: 20px/50px;
            background-clip: padding-box;
            text-align: center;
          }
          .button {
            font-size: 1em;
            padding: 10px;
            color: #fff;
            border: 2px solid orange;
            border-radius: 20px/50px;
            text-decoration: none;
            cursor: pointer;
            transition: all 0.3s ease-out;
          }
          .button:hover {
            background: orange;
          }
          .overlay {
            position: absolute;
            top: 0;
            bottom: 0;
            left: 0;
            right: 0;
            background: rgba(0, 0, 0, 0.7);
            transition: opacity 500ms;
            visibility: visible;
            opacity: 1;
          }
          .overlay:target {
            visibility: hidden;
            opacity: 0;
            display:none
          }
          .popup { position: relative;
            margin: 70px auto;
            padding: 20px;
            background: #fff;
            border-radius: 5px;
            width: 30%;
            
            transition: all 5s ease-in-out; }

.popup .close       { position: absolute; top: 20px; right: 30px; transition: all 200ms;
                      font-size: 30px; font-weight: bold; text-decoration: none; color: #333; }
.popup .close:hover { color: orange; }
.popup .content     { max-height: 30%; overflow: auto; }

/*.popup h2 { margin-top: 0; color: #333; font-family: Tahoma, Arial, sans-serif; }*/

External CSS

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