So I brought to the foreground iPhoto and hovered the cursor over mail, Safari and Finder, finding highlighted buttons in each of those three apps.

Suckage!

As a consequence of posting this page to #macintosh on EFNet I found out that those annoying yellow boxes are hated by many and they are called tooltips and they can be turned off in Safari and I did so. I have not been able to locate knowledge about how to do so with mail.app or iPhoto
Finder-Mail-Suckage
Safari-Mail-Suckage
Safari-Finder-Suckage