CodePen

HTML

            
              <div class="wrapper">
  <div class="content"></div>
</div>
            
          
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↑ Insert the most common viewport meta tag

CSS

            
              .wrapper {
  width:250px;
  margin:25px auto;
  background-image: linear-gradient(bottom, rgb(188,19,190) 13%, rgb(226,46,228) 57%, rgb(36,97,171) 79%);
  background-image: -o-linear-gradient(bottom, rgb(188,19,190) 13%, rgb(226,46,228) 57%, rgb(36,97,171) 79%);
  background-image: -moz-linear-gradient(bottom, rgb(188,19,190) 13%, rgb(226,46,228) 57%, rgb(36,97,171) 79%);
  background-image: -webkit-linear-gradient(bottom, rgb(188,19,190) 13%, rgb(226,46,228) 57%, rgb(36,97,171) 79%);
  background-image: -ms-linear-gradient(bottom, rgb(188,19,190) 13%, rgb(226,46,228) 57%, rgb(36,97,171) 79%);
  
  background-image: -webkit-gradient(
    linear,
    left bottom,
    left top,
    color-stop(0.13, rgb(188,19,190)),
    color-stop(0.57, rgb(226,46,228)),
    color-stop(0.79, rgb(36,97,171))
    );
  
  padding:10px;
  border-radius:20px;
}

.content {
  height:250px;
  width:100%;
  background:white;
  border-radius:10px;
}

            
          
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JS

            
              
            
          
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