title: Width of element with fixed position Bootstrap
body: <p>I got an element with <code>width=auto</code>. When when I add <code>position: fixed</code> to that element, it visually changes its width. How can I keep the aspect of the element after  adding <code>position: fixed</code>? I want a responsive and centered element with position 'fixed'.</p>
  
  <p>This is an example of the problem (class <code>first</code> and <code>first_top</code>) : <a href="http://jsfiddle.net/nWHSH/" rel="nofollow">http://jsfiddle.net/nWHSH/</a></p>