I have an `h1` on which I've defined the following styles:

```
h1
  { text-align: center;
    border: double black 1px;
    padding: 1em;
    margin: 1em;
}

```

Here's a JSfiddle: <http://jsfiddle.net/KatieK/Hs3ZQ/>

I set the border-style to double, but I'm only seeing a single border rendered. Why isn't a double border rendering?