This page attempts to provide help for "Citation Style 1" errors. These errors are caused by the citation template ("Template:Cite") somehow. That template was copied over from English Wikipedia a long time ago, so older help pages over there may be the best resource.
Here's a couple of English Wikipedia links to information which may be helpful:
- w:Help:CS1 errors - an updated version of the page that used to reside ere.
- w:Help:Citation Style 1 - an explanation of what "Citation Style 1" is