title: height of html input element differs, is computed wrong
body: <p>I have a problem with the style of an input element.
  The computed tab of firebug displays the height of the field as 16px though the css value of the height is 18px. As you can see in the screenshot, the input area should be as tall as the button on the right.</p>
  
  <p>Screenshot:</p>
  
  <p><img src="https://i.stack.imgur.com/QVy4b.png" alt=""></p>
  
  <p>The site is mainly a static html recreation of a dynamically generated site. Though I recreated the whole structure with the corresponding clases, names and ids.</p>
  
  <p>The value 16px is never set, I guess it's the browser default, but why is the value 18px ignored?</p>