Property:Has improper value for
From semantic-mediawiki.org
"Has improper value for" is a predefined property that tracks input errors for irregular value annotations and is provided by Semantic MediaWiki. In most cases it is caused by a type mismatch or a value restriction. This property is pre-deployed (also known as special property) and comes with additional administrative privileges but can be used just like any other user-defined property.
This is the page of special property Has improper value for. It lists all pages using this special property. See the help page on special property "Has improper value for"Alerts in case the assigned value to a property is invalid for further information.