If you have the AdBlocker Ultimate extension extension then this is likely a problem with this extension as there have been several reports.

• 1847380 - Adblocker Ultimate preventing pages from displaying correctly

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Hi

I understand that we may have a fix for this problem.

1. Open AdBlocker Ultimate from the toolbar icon and select Settings.
2. Next, select the Filters tab in the page that opens and turn off the Security option.
3. Close the page and then repeat the process, but turning the Security option on.

Does this help fix the issue?