Greetings! I sometimes use the Google Fiber speedtest site to test download speeds:
http://speedtest.googlefiber.net/
I've found the site doesn't fully load in Firefox 64 (64.0 on Ubuntu 18.10 Linux (64-bit) and 64.0.2 on Windows 7 (32-bit)). Could someone here try and see if it works for you? Here's the deal: the page loads, but the test server is identified such that the speed test can't be run.
When I view the same page in Opera or Chromium, the test server is identified and I can run the speed test.
Thanks!