Examine source code of YouHub

{
  "theme": {
    "images": {
      "theme_frame": "headerpersona.png"
    },
    "colors": {
      "frame": "#666666",
      "tab_background_text": "#666666"
    }
  },
  "version": "2.0",
  "name": "YouHub",
  "manifest_version": 2,
  "description": "<a href=\"https://outgoing.prod.mozaws.net/v1/ed91ccfa5864d39fac31a75d4a9dfb62dee8a34dd2c63edca3fa4ed370d6f50c/http%3A//YouHub.org\" rel=\"nofollow\">YouHub.org</a> - Save energy when you use PC"
}