Meta Tags - What Are They & Which Search Engines Use Them? By: Richard Zwicky
Defining Meta Tags is much easier than explaining how they are used, and by which engines. The reason is very few engines clearly lay out what they do and do not look at, and how much emphasis they put on any one factor. So, we’ll start with easy part
Meta Tags are lines of HTML code embedded into web pages that are used by search engines to store information about your site. These "tags" contain keywords, descriptions, copyright information, site titles and more. They are among numerous things that search engines look for, when trying to evaluate a web site.
Meta Tags are not "required" when you're creating web pages. Unfortunately, many web site operators who don’t use them are left wondering why saying "If I build it they will come" didn’t apply to their site.
There’s also a few naysayers in search engine optimization industry who claim that Meta Tags are useless. You can believe them if you like, but you would be wise not to. While not technically "required", Meta Tags are essential.
If you simply create a web site and register URL with search engines, their spiders will visit your site, and attempt to index it. Each search engine operates slightly differently, and each one weighs different elements of a web site according to their own proprietary algorithms. For example, Altavista places an emphasis on description tag and Inktomi states on their web site that;
Inktomi "(...) indexes both full text of Web page you submit as well as meta-tags within site's HTML." Other search engines like Exactseek are true meta tag search engines which clearly state their policy:
"Your site will not be added if it does not have Title and Meta Description tags." They also use keywords tag.
Of course, not all search engines work this way. Some place their emphasis on content. The search engines have over 100 individual factors they look at when reviewing a web site. Some of these factors deal with page structure. They check to see that all 't's are crossed, and 'i's dotted. They note sites that have omitted basic steps, like missing tags.
One reason so many engines de-emphasized meta-keyword tag had to do with spam. There was a time when 'search engine promotion specialists' would cram keywords tags full of irrelevant information. The web site would be selling garbage cans, but keywords tags were chock full of irrelevant terms like "mp3" or "Britney Spears". They figured that if enough people visited their site, some would buy.
So today, to avoid and penalize this kind of abuse, some search engines don’t specifically use keywords tag as part of scoring of a site, but they monitor keywords to ensure they match content in site. The reasoning being that, if tags are irrelevant, they must have an alternate purpose. Is it a spam site? When keywords tags are completely irrelevant to content, some search engines, that don’t specifically use keywords tags, will penalize that web site.
Even for those engines that have downplayed value of Meta Tags, there are situations where Meta Tags gain considerably in importance, e.g. sites with rich graphics, but poor textual content. Unfortunately, a picture is worth 1000 words to you and me, but zero to a search engine. If a site has poor textual content, engines will be more dependent than ever on Meta Tags to properly categorize it.