Examine source code of Windows HD

{
  "theme": {
    "images": {
      "theme_frame": "windows-header.jpg"
    },
    "colors": {
      "frame": "#333333",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Windows HD",
  "manifest_version": 2,
  "description": "Firefox loves Windows! Find Great Wallpapers at <a href=\"https://outgoing.prod.mozaws.net/v1/447c93f6e5c1f7befbf17d2a4c908e8fbd23d571d40e5e93282e2a088719efdb/http%3A//WallpaperWise.com\" rel=\"nofollow\">WallpaperWise.com</a>!"
}