Examine source code of Yamfree

{
  "manifest_version": 2,
  "author": "Savevur",
  "version": "1.0.1",
  "name": "Yamfree",
  "description": "Yahoo Mail free of advertising links",
  "icons": {
    "32": "icon/icon-32.png",
    "48": "icon/icon-48.png",
    "96": "icon/icon-96.png"
  },
  "browser_action": {
    "default_icon": {
      "32": "icon/icon-32.png",
      "48": "icon/icon-48.png",
      "96": "icon/icon-96.png"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.yahoo.com/*"
      ],
      "css": [
        "css/visual_effects.css"
      ],
      "js": [],
      "run_at": "document_idle"
    }
  ],
  "web_accessible_resources": [
    "css/*",
    "font/*",
    "icon/*",
    "js/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b63252ec-5332-4ccc-8bea-cc471a866987}"
    }
  }
}