I just started to check out modx. I see that it has the usual setup for clean url’s...however the result of this is redirecting all 404’s to a page and is being served as 200-file found for non existant pages.
While this seems great and nice and such, it causes serious serach engine problems.
1) All wrong url’s are reported as 200 - file found, therefore search engines will keep adding all 404 pages/url’s to your site---no updates for old non existant pages/wrong url’s.
2) As all 404;s go to one page there is a serious danger of a duplicate content penalty as multiple (200/file found) url’s point to one page.
Documentation: what is a result code and why should I care?
http://gsitecrawler.com/articles/error-404-200.asp
Test yours
http://gsitecrawler.com/tools/Server-Status.aspx