Acorn, Egg,
I can confirm, that there is no difference between browsers. I checked this with a clean new installation of Win10 on a separate machine and my sample works with Chrome the same way as it does with Firefox. After this I deleted Chrome on my main developing workstation and cleared all settings, reinstalled Chrome, compared every setting with the fresh installation of the separate machine. Unfortunately this action was only partially successful, which means the sample still doesn´t work all the time correctly with Chrome, but interestingly it works correctly, when I check it by using Chrome Dev-Tools (F12). Which means 1 of xxx applications on my development machine is able to effect Chrome. This has become a really personal problem now and I do not have the time to do a complete new setup of my main machine. But by the way you helped me with your clarification as I now able to keep this in mind and will double check every change with different computers as well, as a short time workaround.

Dependant on time, I will check your last suggestion too, although the CSS you have prepared is a good compromise, which can do the job.

Thank you again for your support.

Kind regards