The API Help page's CSS file, located at http://sstatic.net/so/all.css, is current returning 404 for me:

<div id="header"><h1>Server Error</h1></div>
<div id="content">
 <div class="content-container"><fieldset>
  <h2>404 - File or directory not found.</h2>

  <h3>The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.</h3>
 </fieldset></div>
</div>

The documentation is still perfectly usable, just a little ugly. Not a deal breaker by any means, but just letting you know.