Hello,
now I have an answer belonging this curious problem.
I asked Jo Bager. I read an article from him
in
c't, which is a German computer magazine.
In this article, the difference of behavior was discussed.
Herbert Braun, a colleague of him, answered: (my translation from German to English)
>
>This is not a Firefox problem. Opera and Safari display the site in the same kind.
>
>The error is in IE:
>
>In the discussed html page, the button is overlaid from an other <DIV> layer,
>and so it is not possible to click the button.
>
>Except in IE, because buttons in IE are placed always in the highest layer (z-index).
>
I looked and
indeed there was a <DIV> box, which had no content in the region of the concerned button.
So thanks for all,
who spent thoughts for this little problem.
Erhy