Error messages that tell you what the problem is so you do not have to call support
Error message that actually tell you what the problem is so you do not have to contact support.
Example: Everytime I tried to add an image to an inventory item, it would just say ERROR when I tried to save, with no further explanation. After spending 30-minutes on hold waiting for support, they told me I had to turn Online Ordering ON in order for the image to save.
It would have been nice to have an error message that said "Error: can not save image because online ordering is not turned on."