WordPress has a few nasty issues with duplicate content which the Robots Meta plugin I wrote can solve for you. In the latest update I just put up, you can now also disable the date based archives if you don’t use them, and the author based archives.
Especially the last one is one that few people realize is there, all the time. Even if you only have one user, and that user’s username is admin, you will have an author archive for the user admin under
/author/admin/. If somebody wanted to do you harm, linking to that would be a nice way to create some duplicate content on your blog.
There’s another new thing in this plugin which you will only see when you’ve upgraded to the soon to be released WordPress 2.3. In WordPress 2.3 URL’s will be canonical, so
example.com/?id=1 won’t work for post 1 anymore if you’ve decided on some form of permalinks, it will in fact even 301 redirect to the correct URL. That new feature of WordPress is a huge improvement in my opinion, however there’s one small problem with it. If your permalink structure does not contain a slash at the end of it, for instance you used
/%category%/%postname%.html, all your archives and pages will not have a trailing slash added to them. This plugin allows you to force WordPress to do that anyway, and redirect to that version of the URL.
So go get the latest version of the WordPress Robots Meta plugin!