HTTPS sites displaying only as text

[MacEachaidh]

I'm running FF 54.0.1 (32-bit) on Windows 7 x64.

Not sure if something got broken in a recent update, but web pages that previously worked fine are now loading only a text version, with all the content and links appearing down the left side of the browser window, undistinguished and overlapping. It looks like the pages' style sheets aren't being applied. This is only happening to HTTPS sites -- any HTTP site seems okay -- but it's happening to every HTTPS site I've thought to try.

Doesn't seem to be a firewall issue, because even with the firewall off (I'm using Bitdefender IS 2017), the problem still remains. The problem doesn't occur with the same sites in IE 11. (I have no other browsers installed.)

I run FF almost vanilla, but I also tried running it strictly without extensions/add-ons, and the problem remains.

Is this a known issue? Is there a known fix?

[DanRaisch]

Clear the browser cache (use menu path Tools->Options->Advanced->Network tab->click on "Clear Now" button.)

Delete any cookies relating to the site(s) involved (Tools->Options->Privacy->Firefox will "Use custom settings for History"->Show Cookies button).

[MacEachaidh]

Thanks Dan. Should have mentioned in my first post I've already done those steps.

[DanRaisch]

I also tried running it strictly without extensions/add-ons,

Do you mean Safe Mode, or just with extensions disabled?

[MacEachaidh]

Safe Mode. I'm never sure whether just disabling extensions completely removes their potential impact.

[DanRaisch]

If no improvement using Safe Mode, do you have the same problem if you create a new profile and test it with no extensions or non-default themes installed?
http://kb.mozillazine.org/Profile_Manager
and
http://kb.mozillazine.org/Creating_a_ne ... on_Windows

[MacEachaidh]

So this is not a common experience?

[dickvl]

You can check in the Network Monitor if CSS files are blocked.
https://developer.mozilla.org/Tools/Network_Monitor
https://developer.mozilla.org/Tools/Web_Console

Just to be sure, you can check that your security software isn't blocking content:
https://support.mozilla.org/en-US/kb/tr ... OWN_ISSUER

[Brummelchen]

problems are never common except its a known bug. but not yours.

https sites as text means that it has mixed content. the styles (css) is not loaded due http w/o s - or wrong cert from wrong site.

turning BD off has no effect because all the drivers are still loaded - you need to uninstall to verify!
but at first you should disable the ssl check in BD
https://www.bitdefender.com/support/wha ... -1090.html
https://www.bitdefender.com/support/how ... -1117.html