title: Size of fixed position alerts in bootstrap
body: <p>I'm trying to design a web page using Twitter Bootstrap with a "floating" (fixed-position) alert at the top, like so:</p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div class="container"&gt;
    &lt;div class="row"&gt;
      &lt;div class="col-sm-12"&gt;
        &lt;div id="top-message" class="container row col-sm-12"&gt;
         &lt;div class="alert alert-danger"&gt;
          Hi there!
         &lt;/div&gt;
        &lt;/div&gt;
      &lt;/div&gt;
      &lt;!-- page content --&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>CSS:</p>
  
  <pre><code>#top-message {
      z-index: 10;
      position: fixed;
      width: 100%;
  }
  </code></pre>
  
  <p><a href="https://jsfiddle.net/zs1f8u6j/" rel="nofollow noreferrer">JSFiddle</a></p>
  
  <p>On smaller screens, this works perfectly:</p>
  
  <p><a href="https://i.stack.imgur.com/UjeuX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UjeuX.png" alt="On smaller screens"></a></p>
  
  <p>However, on larger screens, the alert simply extends out like this:</p>
  
  <p><a href="https://i.stack.imgur.com/fvTU2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fvTU2.png" alt="On larger screens"></a></p>
  
  <p>Removing the <code>width: 100%</code> from <code>top-message</code> wouldn't be an option either, since I need the alert to occupy some width even though the text is small.</p>
  
  <p>How should I design the page so that the alert is maintained in the middle of the page like in smaller screens; for any size of the screen on which the page is rendered?</p>