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When people refer to meta tags, they are talking about the meta description and meta keyword tags. Some search engines may display the meta description as part of the search results, but the meta keywords tags does not appear in search results.
I believe creating page specific meta description tags is worthwhile. I generally do not spend time creating meta keywords tags.
<meta name="Description" content="Search Engine Optimization Book is a SEO blog that provides daily search engine news. SEO Book keeps up with the latest trends in search engine algorithm changes and provides new SEO tips."/>
<meta name="Keywords" content="seo book, seo ebook, seo e-book, seo tutorial, seo tutorial book, search engine optimisation, search engine optimisation tutorial"/>
Many search engines use the meta description as part of the page abstract if the exact search term is found in the meta description tag. Additionally, it may appear in search results if the search engine cannot extract meaningful content from the page copy or if the algorithm believes the meta description will provide a more useful presentation.
This tag should be between a sentence to a paragraph and should not appear keyword-stuffed. Google shows ~ 160 characters from the meta description tag in their search results. The text should read well to the human eye since this tag is still used in many search results pages.
If your description is compelling, it could boost your click-through rates and, thus, deliver you more targeted traffic. The meta description tag can often be used to help craft a good search presentation for your most popular keyword phrases by complementing the page title, targeting alternate versions, and display your brand messaging, all while inticing clickthroughs.

You can look at the search results of various search engines to see what competitors uses and how many characters the engine displays. In the above image Google displayed around 156 characters from the meta description.
Meta description tags should be unique on a per page basis. If you can not make them unique you are better off not adding one than using the same meta description in a section of your site or sitewide.
Some people try to make meta tags sound like an art form. They are not. There are multiple tags that tell a search engine when to revisit or what language it is in. These tags are usually irrelevant and ignored.
Just about the only useful meta tags other than the description and keywords tags are those tags used to PREVENT search engines from indexing your content. Since we usually want our content seen, this article does not discuss robots exclusion meta tags. If you have duplicate content issues or other undesirable pages you can prevent them from getting indexed using robots.txt or meta noindex tags.
Meta tags are only one small part of search engine algorithms. In major search engines, each of the following are typically far more important than meta tags:
If your site does not have meta keyword tags, I would probably not recommend spending the time to add them. If you add meta keywords while you are creating pages, I wouldn’t spend more than a minute on each page. I probably wouldn’t list any more than a few of them per page.
While it is important to optimize for keywords, you do not need to use a meta keywords tag to do so. Most search engines ignore the meta keywords tag.
I usually do not use the meta keywords tag on my pages (as it is not usually very important), but it can help you out if there are many different ways to say your product names and you are not creative enough to cover the permutations in your page copy. Usually it is better to cover the permutations in your page copy with sections like alternate part numbers, etc.
If you use the meta keywords tag, it should be unique for each page upon which you place it. The keywords tag is a good place to put common misspellings, synonyms, and alternate versions of a word.
If a term is competitive, it is going to need to occur in your page copy and/or inbound link text for you to rank well for it.
I offer a free page title meta tag generator. I offer tips on that tool to help you create and optimize your title and meta tags.
Article provided by: SEO Book