Examine source code of Radium Spectra

{
  "theme": {
    "images": {
      "theme_frame": "Ra_2.png"
    },
    "colors": {
      "frame": "#c2c2c2",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Radium Spectra",
  "manifest_version": 2,
  "description": "Emission spectra for Radium, thanks to <a href=\"https://outgoing.prod.mozaws.net/v1/dad43d601b6beea108c33cd81978d6febb8b7cbf7a2e150c0403b990c0d91160/http%3A//student.fizika.org/%7Ennctc/spectra.htm\" rel=\"nofollow\">http://student.fizika.org/~nnctc/spectra.htm</a> for basis image"
}