Examine source code of ID-Alizes.fr

{
  "theme": {
    "images": {
      "theme_frame": "test-firefox1-hautc.png"
    },
    "colors": {
      "frame": "#c4c4c4",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "ID-Alizes.fr",
  "manifest_version": 2,
  "description": "<a href=\"https://outgoing.prod.mozaws.net/v1/e50494e2ef8ba57c6225a5f6534c7b581ee332536093870c34888557566492c3/http%3A//ID-Alizes.fr\" rel=\"nofollow\">ID-Alizes.fr</a>'s logo. Made with Illustrator.\nHope you like it"
}