The nifty little KDE-app Kruler, a screenruler with a couple features that the gnome equivalent lacks, shows up with the standard window decorations in compiz on my standard Ubuntu install. Not exactly what I want.
Here’s how I removed them:
1) Open ccsm
2) Select Window Decorations.
3) Change the “Decoration Windows” line to look like so: (any) & !(class=Kruler)
That’s it. If you want to match for some other windowtypes you don’t need to learn the settings syntax. Just click the plus sign to add a new rule and the click grab and select an active window you’d like to match.