title: HTML5 Input type "number" in Firefox
body: <p>I am working on an app that is only used by a few people in-house, so I feel comfortable telling them to only use Firefox or Chrome, so I can use HTML5.</p>
  
  <p>I was working on a very simple feature:</p>
  
  <pre><code>&lt;style&gt; 
  input:invalid { background-color: red; }
  div.box {
  border-color:#000; 
  border-width:thin; 
  border-style:solid;
  }
  &lt;/style&gt;     
  &lt;input type="number" name="id"&gt; &lt;small&gt;(if the box becomes red, make sure you didn't put a space)&lt;/small&gt; 
  </code></pre>
  
  <p>It works great in Chrome: it becomes red and won't let you submit, without me coding anything else.</p>
  
  <p>Firefox ... not so much. It acts as if I had a "text" type.</p>
  
  <p>Is that a known issue? Workaround?</p>
  
  <p>Thanks</p>