title: Validation: Bad value first for attribute rel on element link
body: <p>I'm using Piwigo photo gallery software and it dynamically generates some code in the head of the page, which displays like this:</p>
  
  <pre><code>&lt;link rel="first" title="First" href="picture.php?/2601/category/37"&gt;
  &lt;link rel="prev" title="Previous" href="picture.php?/2619/category/37"&gt;
  &lt;link rel="next" title="Next" href="picture.php?/2621/category/37"&gt;
  &lt;link rel="last" title="Last" href="picture.php?/2760/category/37"&gt;
  &lt;link rel="up" title="Thumbnails" href="index.php?/category/37"&gt;
  </code></pre>
  
  <p>When I run it through the validator, I get errors as follows:</p>
  
  <pre><code>Line 21, Column 71: Bad value first for attribute rel on element link: The string first is not a registered keyword or absolute URL.
  …" href="picture.php?/2601/category/37"&gt;  &lt;link rel="prev" title="Previous" hre…
  
  Line 21, Column 282: Bad value last for attribute rel on element link: The string last is not a registered keyword or absolute URL.
  …" href="picture.php?/2760/category/37"&gt;  &lt;link rel="up" title="Thumbnails" hre…
  
   Line 21, Column 348: Bad value up for attribute rel on element link: The string up is not a registered keyword or absolute URL.
  …category/37"&gt;  &lt;link rel="up" title="Thumbnails" href="index.php?/category/37"&gt;
  </code></pre>
  
  <p>After some reading, I have come to understand that HTML5 has removed rel up, first and last, though it has kept prev and next. What I don't understand though is what to replace up, first and next with? If I remove them completely, the validator isn't happy with that either.</p>
  
  <p>Does anyone know? Thanks. :)</p>