I have an entire missive on the set up of meta tags, but wanted to take a moment to talk about why they are needed at all. For a long time now they have been downplayed, mainly due to the fact they were and are, much mis-used, to the point where a great many sites have taken to not using them at all. This is an error, a few facts as to why and which ones you must have.
Most engines will not index the site properly without them.
In fact, a great many engines will not even attempt to index you period without them, so downplayed or not, they must be there.
This is the tag that is most abused, which is what led to them begin downplayed. All too often keywords are being used that do not relate to the site itself and or, are not on the pages of the site, even if they do relate. This is often due to the desire not to have massive amounts of text on that front page. There is perfectly good reason for this. The viewer is most often motivated by imagery, not what they read, however the search engines must have text to index the site to where the viewer can find it in the first place, so its a trade off.
Designers, wanting a clean, neat look or at the clients insistence for such a look, design a plain and simple splash page, with a few images and some promotional text, which, while good for the promotion and viewer preference, is often not enough for density of keywords.
Example: Large image of goods
See our large selection of ( short list of goods here ) ... end of page
The keyword tags however are a massive list of every possible goods the site offers and all the combinations thereof, the problem ? The words being used are not ON the page itself. And this is the most reasonable, as at least the goods in question are indeed being offered. There is no way however, for the engine to know this, without "reading" the entire site to find out. They will not attempt this. The assumption will be, its an attempt to spam the engine and treat the site accordingly.
Wanting to keep that clean look, yet have the words on there to be able to use them in the keyword tag, led to hidden text, were the relevant text is "visible" to the engines but not the viewer, which was an attempt to put the text up the engines need, without ruining the look. This led to much abuse however, of folk who put in hidden text that didn't relate to the site at all, but were good keywords to drag in viewers. Now, if you attempt such a thing, the spider will most likely ban the site, rather than index it.
If the tag is not there, what you have available to be indexed, is whatever short bits you have in text on the page, and that's all you have. I cannot count the number of sites I have seen that force the information load onto images and only images, which the engines ignore. No text ? The page may as well be blank as far as the engines are concerned.
Description: Those very important few sentences. Lacking these, the engine must drag, out of context, whatever words happen to be on the page. Which they will often do anyway, depending on the question the viewer put to the engine ( another good reason those first words should give a good idea of what the site or page is about ). Lack of this tag makes it harder for the engines to catalog you and hampers its ability to figure out if YOUR site is the best over all answer to the question put to it.
And again, have a page with almost no visible text and no description in the meta tag ? Whatever you do have on the page is all the engine can and will read.
is yet another that there is a missive dedicated to this alone as to why
you need a good title.
The single most important bit of information your web page contains, as this short bit is what the engines use first to decide what is on the page itself.
No title, and its indexability just dropped to near zero.
These three, along with a proper document
statement, are mandatory. You can, if you want, skip all the rest of them,
but without these, your page may as well not be on the net.