title: background in CSSStyleDeclaration is undefined in Firefox
body: <p>I have a small function that will take a string of css (eg <code>background: red; width: 145px; height: 145px;</code>)
  and return a <code>CSSStyleDeclaration</code> but if I have a <code>background</code> property (and <code>background-color</code> etc) the<code>CSSStyleDeclaration</code> will have <code>background-color</code> etc set as <code>undefined</code> in Firefox.</p>
  
  <pre><code>_parseCSS: function(css) {
    var div = document.createElement('div');
    div.innerHTML = '&lt;div style="' + css + '"&gt;&lt;/div&gt;';
    return div.childNodes[0].style
  }
  </code></pre>
  
  <p>does anyone know what I'm doing wrong?</p>
  
  <p><strong>EDIT:</strong> here's the code that doesn't work with Firefox:</p>
  
  <pre><code>style: function(style) {
      var css = this._parseCSS(style);
      return this.each(this._elem, function(element) {
        this.each(css, function(s) {
          var prop = s;
          element.style[prop] = css[s];
        });
      });
    },
  </code></pre>
  
  <p>the parameter <code>style</code> is the string of css.</p>