Thanks to both of you for letting me know that you do not have the problem. I've sent you a screenshot, Martin. If there is no quick fix, no big deal. Seems to be a problem unique to my situation.

The reason for using the Desktop rather than the Mobile version was that I couldn't find a Search in Forums function in the Mobile version. Maybe that's again a problem that only I have.

Strange indeed - I can't think of a reason why the two header-bars are missing in your screenshot - but of course, our devices are slightly different. But even with the developer-tools I can't "fake" any device or resolution where the bars are missing.

In the mobile version, the "search in all forums" is located in the yellow top bar right on the start page of the forum - there is a magnifying glass at the top right.

Thanks, Martin, for at least trying to reproduce the problem. Apparently it's affecting only me, so no need for any additional effort on my behalf.

As for the mobile version, there is no yellow bar at the top of the forum start page. Also no magnifying glass. Even the three horizontal lines for the menu are not displayed. (I have a screenshot if it's of any interest.) I wonder whether some Firefox setting is causing the problem.