The link in the article page to edit the Wikidata links is of the form:

<a href="//www.wikidata.org/wiki/Special:ItemByTitle/enwiki/John Colter" title="Edit interlanguage links">Edit links</a>

For articles with a space in the name, the space is included in the href, which is invalid. This needs to be properly encoded.

Examples:

http://en.wikipedia.org/wiki/John_Colter

http://validator.w3.org/check?uri=http%3A%2F%2Fen.wikipedia.org%2Fw%2Findex.php%3Ftitle%3D-%26curid%3D1056709%26uselang%3Den&charset=%28detect+automatically%29&doctype=Inline&group=0

Version: unspecified
Severity: normal