If I want to open the YouTube startpage I get shown only links and buttons. Can I do something to change this ?

Certainly not a bug, you just have blocked something.
The possibilities are endless with the newer engines though...
Perhaps the quickest way: Open page "about:config", ignore the warning, and take a look at the BOLD settings. Bold (fat) text means "= not default, set by user".
If they sound like having to do with videos, right-click on them to "reset". That's nothing dangerous, it merely restores the default settings.
Some of those settings will work immediately via about:config, others will need a toggle via menu or a browser restart.

A more brutal way: if you just want a quick test and delete ALL user settings, click
Edit > Configuration > Profile Directory", close the browser, then rename the file "prefs.js" and restart browser.
This will NOT affect bookmarks, sessions, cookies, history, skin single buttons config (except toolbar visibility), macros etc., which are stored in other files. And you can always restore your old settings in prefs.js again, by renaming it back - but there is a risk to lose it if you don't know exactly what you're doing, so make sure you keep a backup copy

And there are still more possibilities that can affect user settings:
especially macros, and "user.js" (but the latter hardly anyone seems to use anyway). Also filetype settings (=mimetypes => F2 > Filehandling by Type), am not quite sure if those are all stored in a separate file or not.



Edited 2 time(s). Last edit at 09/05/2015 04:09PM by siria.

Thank You . I tried the solution with the prefs file . It did not work.
Perhaps it might help that I get an error message when I try to open Youtube.
It means: Secure connection failed. The cecurity certificate is not up do date.
(Fehlercode: sec_error_unknown_issuer). So I make an exception and it goes on.
And beside that , my changes in configuration are not that hard that a browser could not open a page . :-)

I found out it is caused by my adblocker. Strange is- in version 74 the adblocker lets the site pass and in 75 he blocks the site.