Examine source code of Netacad for you

{
  "manifest_version": 2,
  "name": "Netacad for you",
  "version": "1.2resigned1",
  "description": "Change soso",
  "icons": {
    "48": "icons/border-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.netacad.com/*"
      ],
      "js": [
        "borderify.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b0effd5c-5779-4520-b607-f4e86087bdd6}"
    }
  }
}