I think that if you did this,

register_activation_hook(__FILE__,'your_function');
your_function () {
echo '<div id="message" class="updated" ><p>Jürgen's Message</p></div>';
}

It would work out fine. I don't know if my html is going to come out okay here, but you get my point I hope that helps!

"Hello, please have a look at the settings. Thanks"

I wanted to print it through "register_activation_hook()"
But it won't work.
Can you help me?
Jürgen

Personally I miss the fade class that use to fade the message in, back in the old days (before they switched to jQuery). I don't think there is a modern equivalent of that.