Meta Tags And Search Engine Optimisation

There's loads of META tags. Loads and loads again. While I'm writing this and while you're reading it, somebody, somewhere, will be beavering away thinking up good reasons why we should all be using loads more.
Probably.
But for SEO purposes, we only really need to worry about a few of them.

META Tags - the good guys.

There's two you should use, and use them all the time. I think everybody will agree about the DESCRIPTION TAG, an example of which is near the top of the code of this and all my pages, and a further is below.

<META NAME="DESCRIPTION" CONTENT="I always put a description of the contents of the page in here - keywords in first, mind">
Given the general acceptance that engines will only index a certain amount of the content herein, I keep it down to around 150 or so characters.

<META NAME="KEYWORDS" CONTENT="I'll put keywords relevant to the page in here">
and controversial that is too. A lot of folk will tell you the engines no longer read the keywords tag. That seems (at time of writing) to be true of the majority of engines but evidence to the contrary does crop up from time to time. I've always used them and I continue to do so. Opinions do vary as to how keywords should be used in the tag. Some feel, as I do, that the words need be used only once and that the engines will parse the words to make up any needed phrase. Others feel that the phrases themselves should be included in full, separated sometimes by commas or sometimes by a comma and a space. I myself feel that separating single words with a space is fine for our purposes, and would not be critical of a site which did the same thing but with commas. Using both a comma and a space as many sites do, is an unnecessary waste of a precious character as to an engine a space and a comma are both characters.

META Tags - the not-so-good guys.

Robots Text - this is not it and these are not they;
so don't let anyone tell you they are. A Robots text file is a plain text file that sits in the root directory of your site and tells various search engine spiders that they shouldn't index all or certain portions of your site. As a general rule, they do indeed serve their intended purpose in that the engines' spiders will observe the text instructions (more about them here and indeed here).
Unlike these. You just can't depend on these to work as it seems that, mostly, they don't. When on the internet. erring on the side of caution is never a bad idea.

<META NAME="robots" CONTENT="INDEX,FOLLOW">
This advises the spiders to index the page and follow the links contained therein. A waste of time because unless impeded by bad coding (such as broken links) that's what they do anyway.

<META NAME="robots" CONTENT="INDEX,NOFOLLOW">
Similarly, this advises the spiders to index the page but ignore the links on it.

<META NAME="robots" CONTENT="NOINDEX,NOFOLLOW">
This instructs that the spiders should not index this page and nor should they follow the links therein. Curiously, a couple of the engines do actually supposedly follow this instruction. Google and Teoma, to name two (and coming fast from the back with a late run is the brand new MSN engine). Problem is, though, I would suggest, is that, if any engine doesn't follow this instruction, and then other engines index that engine's index, and then another engine does the same, and so on and so forth....you see my point? If you don't want your pages spidered, best not put them on the web. A simple solution. Mind you, there's desktop search now, apparently with a new raft of security issues, so perhaps it's best not to write them at all!

<META NAME="robots" CONTENT="NOINDEX,FOLLOW">
You've probably got the hang of this by now; this advises that while the spiders may not index the page they can and should follow the links in it.

If you do want to find more information on what the real robots text files can do, you could do worse than to try here but I have to warn you, it gets a little wordy out there.....

<META NAME="REVISIT-AFTER" CONTENT="7 Days"
While we're on the subject of robots, this last advises the spiders to return, revisit and re-index the site in, in this instance, 7 days.

they won't. Not because you tell them to, anyway. The best way to encourage frequent revisits by spiders seems to be by refreshing and rebuilding your content every few days or so.

These below won't do you any specific harm but I'd personally leave them all out. Some of them had a purpose at one time or other, others were presumably brought into being as they were intended for purposes that never materialised. I get by, as do many, without them.

The DUBLIN CORE tags

If I were to describe the purpose of these tags I'd have to resort to paraphrasing folk more knowledgeable than myself, so I may as well direct you to a site which can explain them in depth. Here you may thrill to such utterances as "Usage Board announces new DCMI term 'Provenance'", and "Pre-conference '<METAdata for Interoperability in the Global Corporate Environment'". I'll be in the pub, myself.

The Wayback Machine Internet Archive Tags

Wayback Machine Exclusion tags look like this;
User-agent: ia_archiver
Disallow:/
Hopefully if you include these tags in your header then your existing pages will be removed and future pages will not be included in The Wayback's index. I say hopefully because, although that's the theory, I don't know anyone who's tried it.

New kids on the Block; Google/DMOZ tags

They look something like this;
<meta name="ROBOTS" content="NOODP">
and what they do is they stop the HOME PAGE, let's just stress that this is only for the HOME PAGE of your site, snippet in Google being taken from the DMOZ description which can easily get to be out of date and can be a bitch to get altered by the idle slackers at DMOZ, the Idea Whose Time Has Gone. So, then. if you use this meta tag at all, you'll only be wanting to use it on your HOME PAGE. Geddit?

So, then. META tags. What works for me is using the two I've indicated and, mostly, ignoring the rest. My experience, however, may not necessarily be yours and you may well come up against these or others in contexts and combinations that I never have nor have I ever envisaged, so you do need to make up your own minds about what to do.

SEO META TAGS INFO

META Tags, and why you probably shouldn't be using so very, very many!

META Tags - the good guys.

META Tags - the not-so-good guys.