<div class="box"></div>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
    <script src="script.js"></script>
.box {
           width: 150px;
    height: 150px;
    margin: 30px auto;
    margin: 30px auto;
    background-color: blue;
  }
$(function() {
  $('.box').mouseover(function () {
    $(this).fadeOut(2000);
  });
 
});

External CSS

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External JavaScript

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