Top Post in the Window jumps in Front of the Navigation.

I have a very disturbing behaviour if I hover above a Post on the Top of the Window it jumps in Front and hides the Navigation Bar.
Is that behaviour wished or I am the only one for whom it happens?

Do you have a screenshot please?

Fred

I've tried to take a Screenshot but it won´t work. I will send a Handy Photo.

It does not happen anymore.
Thanks,