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HTML

            
              <div class="box">The width of this box is 440px, even though it is defined at 400px in the CSS.</div>
            
          
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CSS

            
              .box {
  margin: 0 auto;
  background-color: aquamarine;
  width: 400px; 
  height: 400px;
  padding: 20px;
}
            
          
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JS

            
              
            
          
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