WordPress 3.1 needs SEO fix to make category links canonical
WordPress 3.1 is great news in many aspects, but not for SEO. If your theme adds categories to a menu (which most themes do), these menu links are changed with WordPress 3.1. This is really bad for your SEO. What Google has indexed as http://yourcoolblog.com/?cat=1 is now with WordPress 3.1 linked to as http://yourcoolblog.com/?category_name=[categoryname]. This is true also for the links that most themes display for single posts, saying: Posted in: [categoryname]
- you no longer have any links on your site to the categories that Google has indexed, and these search results will of course loose their ranking on Google.
- you now have the same content displayed on another URL, which Google will consider duplicate content.
After updating to WordPress 3.1 you really need to use so called Search Engine Friendly URL:s. You need to be on a server that can handle rewrites and you need to use Permalink Settings.