I find this message a bit hard for end users. Maybe this is due to the fact that I'm not native speaker.
I would improve from the old version to the new one:
- Old: The structure cannot be deleted because it is required by one or more structure links.
- New: The structure cannot be deleted because it is being used by one or more web contents.
To test it:
- Create a structure
- Create a web content based on it
- Try to remove now the structure