I have a few very simple beamer slides, which are built up this way:
A short introducory text
A picture, which is almost the same in all slides
Unfortunately, the introducory text is sometimes one line, sometimes two lines and sometimes three. Therefore the picture gets always a little bit shifted in its vertical position. Since this is a presentation, I would it like to have it fixed on a certain position, so that it doesn't change when loading the new slide.