title: Using cm/mm on the CSS of a web app that replicates paper interaction is a good practice?
body: <p>I am building a web application that interact with documents for later printing. In some points is similar to Google Docs. I am considering using cm/mm on the CSS of my documents pages because it will help me on the document generation. Example:</p>
  
  <pre><code>// A4 size
  .page {
     width: 210mm;
     height: 297mm;
     margin: 2cm 5cm; 
  }
  </code></pre>
  
  <pre><code>&lt;div class="page"&gt;
    ...
  &lt;/div&gt;
  </code></pre>
  
  <p>What are the main issues of following this approach?</p>