Forum:Can you add text to a page that will only be visible in edit mode?

I'm sure I've seen TEXT somewhere on a wikia and seen it working, but that didn't work for me.

The main page of my wikia has pictured buttons for main characters, seasons etc and the picture on each button has to be in a 4:3 ratio to fit the borders but people don't know this and keep changing pictures, adding buttons etc with the wrong dimensions so I was hoping there would be a way to warn about this on the page itself but not have that warning visible unless your editing it. Thanks in advance. -- Lyco499 (talk ) 00:23, February 29, 2012 (UTC)