Examine source code of qc.photos

{
  "manifest_version": 2,
  "name": "qc.photos",
  "version": "1.5",
  "description": "Adds a qc.photos button to the CSSBuy item page. Not affiliated with qc.photos",
  "content_scripts": [
    {
      "matches": [
        "*://*.cssbuy.com/item-*"
      ],
      "js": [
        "inject.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8f539d97-1c8b-400b-b585-3cd057a0d1e3}"
    }
  }
}