Examine source code of Guide Trail

{
  "theme": {
    "images": {
      "theme_frame": "guide-haut.JPG"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#000"
    }
  },
  "version": "2.0",
  "name": "Guide Trail",
  "manifest_version": 2,
  "description": "<a href=\"https://outgoing.prod.mozaws.net/v1/4da98db1ab9b497be8a3fb4ee107e1d2cef9c9f81bdd52b8509ac906a074856c/http%3A//www.guidetrail.com\" rel=\"nofollow\">www.guidetrail.com</a>"
}