title: What does "canonical order" mean with respect to CSS properties?
body: <p>MDN's pages about CSS properties (<a href="https://developer.mozilla.org/en-US/docs/Web/CSS/display" rel="noreferrer">example</a>) and some of the CSSWG's specifications (<a href="http://dev.w3.org/csswg/css-flexbox-1/#flex-property" rel="noreferrer">example</a>) make reference to the "canonical order" of the property.</p>
  
  <p>For example, MDN says the canonical order of <code>display</code> is:</p>
  
  <blockquote>
    <p>the unique non-ambiguous order defined by the formal grammar</p>
  </blockquote>
  
  <p>and the CSSWG's flexbox spec says the canonical order of <code>flex</code> is:</p>
  
  <blockquote>
    <p>per grammar</p>
  </blockquote>
  
  <p>Every CSS property seems to be listed on MDN as having a canonical order; canonical order is also mentioned in the entertaining <a href="http://dev.w3.org/csswg/css-module-bikeshed/" rel="noreferrer">CSS Foo Module Level N</a> specification that CSSWG uses as a template for new property specifications.</p>
  
  <p>What does this mean, and where is the meaning specified (if anywhere)? I haven't managed to track down a definition of the term online, nor can I think of any obvious guesses.</p>