Examine source code of Warning

{
  "theme": {
    "images": {
      "theme_frame": "warnnningg.jpg"
    },
    "colors": {
      "frame": "#bfbfbf",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Warning",
  "manifest_version": 2,
  "description": "A collection of silly warning sighns to add humour to your firefox."
}