thanks, that works (not on my firefox, but edge accept it !).
but I still think this should be an image option, so we can keep some sort of ‘wysiwyg’ view of what we’re doing. There is actually a mouseover option in the image/advanced/animation section… too bad we get only a zoom in/out option in there.

Thanks anyway !

Sorry to wake up this old post… but I don’t understand your answer to Robert’s question and can’t find another easy way to do that simple effect :
How to make a rollover effect with 2 same-size-images ?

The best way would be to have an option in the media/image toolbox or create a “image rollover” in the same section… but you talk about an automatic option… what’s that ?
Or maybe you can make a quick css tutorial please ?