title: What is the cookie dot rule?
body: <p>I am using Google Analytics and Google Website Optimizer together.
  On our development rig I suddenly realized that some cookies were set twice.</p>
  
  <p>The GA cookies:</p>
  
  <pre><code>__utma
  __umtb
  __utmc
  __utmz
  </code></pre>
  
  <p>where all set both by GWO and GA. I had only expected to see one set of these cookies. GWO set them with a dot in front of the domain name:</p>
  
  <blockquote>
    <p>.dev.example.com</p>
  </blockquote>
  
  <p>While GA set them as:</p>
  
  <blockquote>
    <p>dev.example.com</p>
  </blockquote>
  
  <p>I tried to google this and read something about it in <a href="http://www.ietf.org/rfc/rfc2109.txt" rel="noreferrer">RFC2109 HTTP State Management Mechanism</a></p>
  
  <p>Searches for it here on SO, results in a number of answers referencing the "cookie dot rule", but I still don't really get it.</p>
  
  <p>What exactly is that rule and which implications does it have?</p>