What is the proper English term for placeholder messages that you find in software, in the following format:
- "No Search Results"
- "No Message Selected"
- "Unable to Connect"
- "Nothing to Show"
These messages are replaced by content when the content becomes available to show. These informational messages act like titles that may or may not have additional more explanatory text underneath - hence the title-case.
These aren't sentences, are they phrases, fragments, etc?