When I first started blogging back in 2007 it was considered a good practice to use tags on your blog posts. One would uses as many tags as possible (while keeping them relevant to the content of course). The idea was that these tags provided that many more avenues by which readers or people using search engines could find your content.
The same strategy was also applied to categories. You would add each post to as many relevant categories ad you felt comfortable with. Three to six or more categories per post were common and the number of tags would often go even higher.
Then both the categories and tags would be listed in the sidebar which would of course, appear site-wide.
Things have changed over the years. Today, given the Panda and Penguin updates as well as plain old concerns over duplicate content, these old tactics aren’t such a good idea anymore.
The main reason is the duplicate content issue. Each tag and category added to a post creates an additional url path by which it can be found. Using canonical urls helps by identifying which one is the actual permalink to the article itself however all those other paths that lead to it are still a problem. Essentially you’re creating duplicates of your own content.
This is why when I started this blog I decided that I would not use tags at all. No tags in posts cuts drastically the number of urls that lead to an individual post. No tags also means there is no reason to take up space in my sidebar with displaying a tag cloud.
Another thing I decided is that while I would use categories to group related posts somewhat I would not use more than one category per post. I simply decided that each category would be broad enough to cover a wide range of sub-topics. This way I will also keep the number of categories to an absolute minimum.
Thirdly, in order to prevent search engines from seeing those categories as duplicate content, I decided that category links would all have rel=”nofollow” on them.
Search engines will still be able to spider all of my content but between the use of canonical urls and adding nofollow to categories I insure that I’m not inadvertently duplicating myself. This also makes for what I believe is a cleaner sidebar.
A fourth thing is that I decided not to add a calendar widget. Again this is because the archive links in the calendar provide yet another route to each post. This eliminates more duplication and also frees up more sidebar space.