What is the map in my browser - what technology

Thank you Gnonthgol for your answer.

First I checked again my Opera settings, paying special attention to anything related to JavaScript. But I could not see anything wrong.

Then, from your encouragement, I reset my Opera to its default settings, basically sacrificing all my personal preferences. Sadly that made Opera very plain and ugly but did not change the empty-map-syndrom.

Finally, going once more over all the settings, I discovered that OSM is the only website which ever made an entry (or did I make that through some typo or unnoticed shortcut?) in the section:

Preferences / Advanced / Storage in the list headed "webpages using persistant storage".

That felt wrong to me, especially if OSM somehow persistantly stored "nothing". So I just deleted this entry and voilà, the tiles started pouring in. I am glad, because our internet connection is slow here and the Opera Turbo feature often helps a lot.

So thanks again. Problem solved. Do I need to click somewhere to mark it "solved" officially?

I will vote now, because your info about OpenLayers and JavaScript is exactly what I had wanted.

Hello Screentosmall, please post your words od f thanking not as a new answer to your original question, but as a comment to the answer of Gnonthgol, because this website is not organized as a forum with chronological entries -> each answer will be voted and displayed e.g. by the number of votes. So can you go to your "answer", choose "more" with the little black triangle and choose "convert to comment" ?

And yyou can mark an answer to one of your question by klicking the symbol ("accepted") under the thumb up / thumb down symbols.

Hello stephan75 - thank you for the friendly correction (with help how to do it better next time and how to fix it this time). I believe I got it now.