his is a introductory guide to "tags" on Technorati, the blogosphere search engine, which started using them in mid-January 2005. It's a practical introduction rather than a tutorial (ending with some personal thoughts about tags), but I'll summarise the basics about Technorati tags and how to use them in your own blog posts - stuff I've learned from digging around, playing around and, as you'll see later, much tearing out of hair. I do assume knowledge of basic HTML (for which see e.g. this or this), but if anything needs to be made clearer or expanded upon, please post a comment and I'll try to help.
What's a Technorati tag anyway?
A Technorati tag is a keyword or category used to describe the subject matter or topic of a blog post. For instance, I've labelled my post about ID cards with the tags Identity Cards, ID Cards, Government, Politics, Society, Privacy, Human Rights, Identity Theft, Crime, Hackers, Terrorism; whereas for my post on the rather rude interpretation one-track minds can give to ambiguously-worded Google Groups FAQs, I've used the tags Humor, Humour, Funny, and Dirty.

So, Technorati tags are like the tags with which people label their photos at Flickr, the free photo management/sharing site (e.g. using the tag "Cat" for a photo of a cat). Or like the tags used to categorise bookmarked Webpages at Del.icio.us and Furl, the services (also free) which enable you to bookmark Web pages, organise/tag them and search your bookmarked Webpages from any computer (Furl even saves a copy of the Webpage on their servers). In fact, due to a hookup with those sites, when you go to Technorati and view their page for a particular tag, you'll see not just blog posts using that tag (e.g. "Funny"), but also any pics and links to Webpages which have been given the same tag by users on Flickr, Del.icio.us or Furl.

You can tag (i.e. keyword) a post with anything you like. You can even make up a tag which didn't exist before anywhere (such as my "Gnashing of Teeth" tag for one of my earlier posts) - and, theoretically, they'll still index it and display it on their tag pages. (I say "theoretically" because I had real problems getting any Technorati tags to work - see this post and this post - but fortunately David Sifry the Technorati boss picked up on it (see his comment at the end of my previous post), and, miraculously, Technorati tags are now working for my blog - as of last night. It's odd because it's been about a week since I posted or tagged those posts - why did it take so long for them to show up on the Technorati tag pages, when the Technorati's info page on tags says that, after pinging them, "Your post should appear on the page in a few minutes (up to an hour during periods of intense activity)"?)
How do you view a Technorati tag page?
To see what blog posts, pics or Webpages have been tagged with the keyword of, say, "Privacy", just go to the URL "http://technorati.com/tag/Privacy". (Or go to Technorati first, and in the search box search for "tag:Privacy" - don't include any quote marks, or any space after the colon). This works for any keyword you like; for "Privacy" just substitute, for example, "Politics" (or indeed "Latex", if you prefer, and who can blame you). Be warned (and be patient): Technorati tag pages can sometimes take an age to load, even on my 1MB ADSL connection.

Note: tags on Technorati are not case-sensitive, so either capital letters or lower case letters are OK. The format above is recommended on Technorati's site for use when tagging your blog posts (the method is explained below). But when you're searching for a tag, at least, it doesn't seem to matter if you use a "www" in the URL or not, or if you use "tag" or "tags" in the URL - the results are still the same. So I believe that when tagging posts also, it doesn't matter - I've seen blogs on Technorati tag pages which have been tagged using "www" and "tags", and obviously they've still been indexed.

What's the point of using Technorati tags in your blog?
Well, first, to get your blog posts onto Technorati's tag pages in an organised, structured way - and also the tag pages of other blogosphere search engines that recognise tags, like Icerocket. That means people searching or browsing through those tag pages will be able to find your blog posts - more exposure, more traffic, hopefully more readers for your blog.

Also, these tag pages often get indexed on Google, and Technorati tag pages commonly appear quite high in Google search results lists due to the high number of blog posts pointing to those tag pages. So, if your blog is linked to from a tag page, someone searching Google is again more likely to come across your posts.

For other possible uses of Technorati tags, see below.
How do you use Technorati tags in your blog?
That's the 64 million euro question. If your blog platform already supports categories and RSS/Atom (e.g. WordPress, Movable Type or TypePad), just assign categories to your posts and publish via RSS/Atom, and you're laughing - Technorati will automatically use those categories from your feed for its tags. (Though note that Technorati tags are more flexible than the broad "categories" used in many blogs - they can be anything from general categories to very specific individual keywords.) UPDATE: in Blogger Beta, which made its debut in late 2006 and is now out of beta as New Blogger, Blogger introduced a new feature called "Labels". Labels essentially operate in the same way as categories on Wordpress etc, so you no longer need separate tools to use categories and, more importantly, Technorati tags, see this post.

If you want to include tags manually on your blog, you're still laughing, because you should be able to make up any tags you like, use them in your posts, and Technorati should include them on its tag pages.

How do you do that, then? Well, according to the Technorati help page on tags, all you have to do is insert this sort of markup into your post (using the privacy example):

Privacy

The important bits to include are those I've put in bold - the "rel="tag"", and the "/privacy" at the end of the URL, in order to get the post (1) recognised by Technorati as tagged in the first place, and (2) filed under "Privacy" on their tag pages.

The "href" URL could in fact be for any site at all, not just Technorati's, as long as the URL ends in a backslash followed by the name of the tag you want (though, if nothing else is suitable, then the Technorati page for that tag may be the easiest choice). To adapt one example Technorati themselves gave, you could use

iPod Stuff

for a post to be tagged with "iPod" and show up on their iPod tag page (but it will NOT be tagged "iPod Stuff"). In other words, you don't have to link to Technorati for your tagged post to show up on Technorati's tag pages.

Tip: if you want to use a tag which consists of more than one word, like "Customer Service", Technorati say to use a "+" symbol between those words in the "a href" bit (although I've found that a simple space works just as well, check out the contrast between my first two tags at the end of this post - both should work, but "+" is safest). Example:
Customer Service
You can have more than one tag for a post. In my case I've listed the tags with that code at the very end of each post, see e.g. the end of the ID card post example. I've deliberately included both singular and plural versions of tags and similar terms to try to help people looking for this kind of information find my post, for reasons I go into further below - and you might consider doing that too.

The tag markup could be included in the main part of the post instead, it shouldn't matter, as long as it's in the body of the post (and not, e.g., your blog's sidebar); I just find it easier to keep all my tags together at the end of the post.