title: CSS centering with 100% width
body: <p>I'm trying to center all the content of a page so that when you adjust the size of the browser, the content moves along with the adjustment. I use the CSS code:</p>
  
  <pre><code>margin: 0px auto;
  width: 670px;
  </code></pre>
  
  <p>However, I want a colored header to cover 100% of the width, while the text within the header adjusts with the rest of the page. How do I simultaneously do these two things?</p>