title: W3C validation error with image width
body: <p>I need an image to resize to the full width of my webpage. This works fine with the following HTML/CSS:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>#logo{
    position: fixed;
    top: 0;
    left: 0;
    min-width: 100%;
    z-index: 3;
    opacity: .8;
  } </code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id="logo"&gt;&lt;img src="/logo.png" alt="logo" width="100%"&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>However W3C validation picks this up as an error. "Bad value 100% for attribute width on element img: Expected a digit but saw % instead."</p>
  
  <p>I tried this alternative, but now the image does not resize of course:</p>
  
  <pre><code>&lt;div id="logo"&gt;&lt;img src="/logo.png" alt="logo" width:100%;&gt;&lt;/div&gt;
  </code></pre>
  
  <p>How do I retain the same effect while still passing the W3C validation? It is the only error on my entire page, and I know it doesn't really matter, but there is bound to be a solution I am overlooking.</p>