Examine source code of Contra Bars

{
  "theme": {
    "images": {
      "theme_frame": "Header.jpg"
    },
    "colors": {
      "frame": "#666666",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Contra Bars",
  "manifest_version": 2,
  "description": "Works best with Firefox 3 default persona - small icons option on Mac OS X.\n\nKnown Issues:\nIt may not display correctly on other platforms and/or without the aforementioned configuration."
}