CodePen

HTML

            
              <img src="http://placekitten.com/20/20" />
<img src="http://upload.wikimedia.org/wikipedia/commons/thumb/d/de/Image-loading.svg/20px-Image-loading.svg.png" />
            
          
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CSS

            
              img {
  width: 200px;
  height: 200px;
}
            
          
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JS

            
              
            
          
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999px
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