Opening Firefox at startup

[Charles Trois]

A simple question.

KDE applications (such as Konsole, Konqueror, Kate=8A) reopen at startup,
provided they were in action at shutdown.

But other applications (I am thinking of Firefox) do not; is there not a
little configuring to do so that Firefox opens up too? I did not find a
dialog option that would do it. Perhaps I did not look closely enough.

I should be grateful for all hints.

Charles