The meta description tag is a portion of Hypertext Markup Language (HTML) code -- HTML is a text description language used for formatting and displaying documents on the World Wide Web -- that appears at the top of a Web page. It contains one or two descriptive sentences, usually less than 200 words, which summarize the content of the page. The meta description tag is supported by all major Web browsers
What is a Meta Description?
Meta description tags, while not important to search engine rankings, are extremely important in gaining user click-through from search engine result pages (SERPs). These short paragraphs are webmasters opportunity to advertise content to searchers and let them know exactly what the given page has with regard to what they’re looking for.
The meta description should employ the keywords intelligently, but also create a compelling description that a searcher will want to click. Direct relevance to the page and uniqueness between each page’s meta description is key. The description should optimally be between 150-160 characters.
<meta name"description" content="Here is a description of the applicable page">
Definition
A description meta tag appears between the "<head>" tags of a Web page and contains a short description of that page. The description on the home page of a site might contain an overview of the site itself. Users won't see the meta description while they're on your site, but it may appear as a search result "snippet" if it contains the search keywords. You can see the meta description of any Web page by viewing the page's source code.
Minimum Description Size
There is no minimum required size for a description tag, and a tag of just 10 characters wont "break" anything. Even pages without a description will still be indexed and appear in search results. If a user searches for unique keywords in your short description, Google will still use your description in the search result snippet, filling out the snippet with body text from your page. However, Google Webmaster Tools will flag pages with a description under 50 characters long on its "HTML Suggestions" page and suggest that you ensure your descriptions accurately describe your site's content.
Optimum Description Length
The length of a description tag can also be problematic if it's too long. Search result snippets have a fixed maximum length of 150 to 160 characters, depending on the search engine, so meta descriptions longer than that may be cut off on a results page. It can therefore be said that a meta description tag should be between 50 and 150 characters long to appear most consistently within search results.
Best Practices
Google highly recommends that you create meta descriptions that accurately describe the content of the corresponding pages. One short, well-crafted sentence can persuade a user to click through to your page. However, while for the vast majority of pages a description is helpful, some pages that can be found with a "long tail" of three or more keywords might be better off without a meta description at all, so that the keywords are more likely to appear in the search result snippet.
