Examine source code of Groupon

{
  "theme": {
    "images": {
      "theme_frame": "persona_header2.jpg"
    },
    "colors": {
      "frame": "#333333",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Groupon",
  "manifest_version": 2,
  "description": "Groupon - One ridiculously huge coupon each day, on the best things to eat, see, do and buy in your city.\n\nGo to <a href=\"https://outgoing.prod.mozaws.net/v1/060b1e889e6c21efc19cba7b8a03786942ad2ac8388378ee5bd70b136f0a47be/http%3A//www.groupon.com\" rel=\"nofollow\">www.groupon.com</a>"
}