Hey Papito,
Sorry for so little info, I'm not allowed to post links yet so I can't.
Thing is there are so many ways to do it that I've never used the same one twice. I depends on your need for each site.
I really just google it each new site to find the code for it.
There are newer and better options each time.
Try Googling "css popups" or "css tooltips".
you can find a whole lot of ways to do it, with instructions and code.
Luck
