Display a RANDOM div when page loads

Very new to coding and Javascript but think I have no choice but to learn to do what I want!

I have a bunch of divs, all with the same css, displayed on one webpage... I want the page to display only 1 div at a time and change randomly each time the page is refreshed (and have a button to refresh the page and thus display a new div).

Thanks in advance for any help!!

Matt @onthematt