sometimes a css property can't be applied due to an error. We mark such properties with yellow triangle but there is no specific info about the root of problem. Sometimes it just a property specific to another browser like -moz-* properties or a standard property which just was wrongly named or has wrong value. It'd be nice to have a tooltip with an suggestion about the problem in css sidebar panel
the same thing will be very helpful for newbie web developers in free text editing mode
*** This bug has been marked as a duplicate of bug 50638 ***