title: Ensuring that a font works for MathJax on untested machines
body: <p>In the stylesheet for my website I have</p>
  
  <pre><code>.mi, .mo {
      font-family: 'Charter', 'MathJax_Math' !important;
  }
  </code></pre>
  
  <p>Setting aside for the moment whether this will always produce satisfactory results for users when an ideal version of Charter is present (so far it does for me), is there a way to ensure that this will have the same effect on machines that I can't test it on. Clearly this fails gracefully for users that lack Charter entirely, but what I wonder is whether the there are Charters in wide use that lack the features that make my version work. </p>
  
  <p>Are there versions of Charter that are better or worse for rendering MathJax? If so how can a locate and test them, or perhaps exclude versions that are less capable?</p>
  
  <hr>
  
  <p>Note this is not a question about downloading Charter along with the pages. If a user doesn't have Charter, he probably isn't attached to it and will be fine with MathJax's default font. What I want to be sure of is that a user who has Charter gets MathJax as Charter, but that users with "poor" Charters (if they exist) aren't punished.</p>