Cover example bug in firefox

Created by: mahnunchik

New "Cover" example are buggy in firefox.

"application": {
    "name": "Firefox",
    "version": "26.0",
    "userAgent": "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:26.0) Gecko/20100101 Firefox/26.0",
    "supportURL": "https://support.mozilla.org/1/firefox/26.0/Linux/ru/"
  }