The keywords and phrases you use in your Meta description tag may not  affect your page's ranking in the search engines, but this tag can still  come in handy in your overall SEO and social media marketing campaigns.
What Is the Meta Description Tag?
It's  a snippet of HTML code that belongs inside the <Head>  </Head> section of a web page. It is usually placed after the  Title tag and before the Meta keywords tag (if you use one), although  the order is not important.
The proper syntax for this HTML tag is:
<META NAME="Description" CONTENT="Your descriptive sentence or two goes here.">
If  you're using a content management system (CMS), look for a field to  fill out that's called Meta Description, or possibly just "Description."
Many  years ago, the information contained in a Meta description could  slightly help a page rank highly for the words that were contained  within it. Today, neither Google, Bing, nor Yahoo! use it as a ranking  signal.
In other words, whether you use your important keyword  phrases in your Meta description tag or not, the position of your page  in the search engine results will not be affected. So in terms of  rankings, you could easily leave it out altogether.
But should you?
There  are 3 important ways that Meta descriptions are being used today that  make them an important part of your SEO and overall online marketing  strategy:
- They can be used as the description (or part of the description) of your page if it shows up in the search results.
- They are often used as part of the descriptive information for your pages when Google shows "extended sitelinks" for your site.
- They are often used as the default description in social media marketing links such as Facebook and Google+.
Let's look at each of these in more detail.
1. Meta Descriptions in the Search Results
People  often think that whatever they put in their Meta description tag will  be the default description that the search engines use under the  clickable link to their site in the search results. While this is  sometimes true, it's not always the case.
Currently, if you're  searching for a site by its URL (for example www.highrankings.com)  Google tends to use the first 20 to 25 words of your Meta description as  the default description in the search engine result pages (SERP).  However, if you have a listing at DMOZ, also known as the Open Directory  Project (ODP) and are not using the "noodp" tag, they may default to  that description instead. (Do a search at Google for www.amazon.com to  see an example.)
Bing and Yahoo!, on the other hand, don't always  default to the Meta description tag for URL searches. Sometimes they  do, and sometimes they don't. A search for www.highrankings.com at Bing  or Yahoo! shows content from my home page as the description rather than  the contents of my Meta description tag.
Of course, real people  aren't typically searching for a site by URL, so what the search engines  show for those types of search queries is not as important as a true  keyword search. So don't get hung up on what you see when you search for  your site by its URL or if you're doing a "site:command" search to see  how they're indexing your pages.
Instead, go to your favorite web  analytics program and find the keyword phrases that are currently  bringing you the most traffic. Then see what your description looks like  at Google when you type in those keywords.
And surprise! What  you'll find is that your search results description will be different  for every search query! You may see any combination of the following  used:
- Your entire Meta description tag text as the complete  description (typically if it's highly relevant and contains no more than  25 words).
- A full sentence pulled from your Meta description  tag, but not the entire Meta description (if it contains more than one  sentence).
- Text from one part of your Meta description mashed together with text from another part of it (if it's more than 25 words long).
- Some text from your Meta description mashed together with some text from the page.
- Some text from your page mashed together from some other text from your page (nothing from the Meta description).
Some of the circumstances that cause Google to not use text from your Meta description may include:
- The information in the Meta description tag was not specific to the page it was on.
- The  search query used some words that were not in the Meta description, but  those words (or some of them) were used in the page content. This  includes words that Google considers somewhat synonymous, such as "copy"  and "copywriting" or "SEO" and "search engine optimization."
But  even the above are not hard and fast rules. Google doesn't always use  all or part of the Meta description even when the exact search phrase  was contained within it – especially if the search query is also  contained within the content of the page. Suffice it to say that there  are no hard and fast rules for when Google will show it and when they  won't.
My recommendation is to always use description tags on any  pages where you get search engine visitors (or hope to get them). Make  them very specific to the page they're on by describing what someone  will find when they click through to the page from the search results,  while also using variations of your targeted keywords.
Because  Google will show only show around 20 to 25 words as your description,  many SEOs recommend that you limit this tag to a certain number of  characters. In reality, however, you're not limited to any specific  number. Your Meta description tag can be as long as you want it to be  because Google will pull out the relevant parts of it and make their own  snippet anyway.
For instance, if you're optimizing a page for 3  different keyword phrases, you could write a 3-sentence Meta description  tag, with each sentence focusing on a different phrase. You could  probably even insert more than 3 phrases in those sentences if you're a  good wordsmith. The idea, however, is not to stuff this tag full of  keywords, but to write each sentence to be a compelling marketing  statement – a statement that naturally uses the keywords people might be  typing into Google to find your site.
2. Meta Descriptions and Extended Sitelinks
These  days, Google often uses the first few words from your Meta description  tag when they create the "extended sitelinks" for your website. But this  too is not set in stone and is highly keyword dependent. You'll see  different sitelinks and different descriptions showing up depending on  the words a searcher used at Google.
As an example, if you do a search for "High Rankings" at Google, you'll see my sitelinks for that search query.
At this moment, Google is showing my home page as the top result with 6 inner pages beneath:
- Forum home page: Description is from DMOZ/ODP. This page has the generic Meta description that is on every page of the forum.
- Link building forum home page: Description is content pulled from the page that uses the words "High Rankings" in it.
- SEO articles page: First part of Meta description.
- Newsletter home page: First part of Meta description.
- SEO/SEM resources page: First part of Meta description.
- SEO classes page: First part of Meta description.
For  the most part, they're using the first part of the Meta description as  the sitelink snippet, but not always. You may have noticed that I  optimized those Meta description sitelink snippets that are showing by  front loading them so that the first 5-7 words or so are a short  description of what the page is all about.
But here's the rub. Do  a Google search for "Jill Whalen SEO." You should still see sitelinks,  and you'll even see some of the same ones as with the previous query,  but some of the descriptions are different:
While the forum home page shows in both, this time Google has pulled  text from the page rather than using the DMOZ/ODP description. This is  likely because this search query had the word "SEO" in it while the  other one didn't. The SEO articles page also shows up here, and it is  using the same Meta description snippet as the High Rankings query. The  other sitelinks are different from before, with 3 out of 4 using the  Meta description.
As you can see, while you do have some control  over your sitelink descriptions via your Meta description tag, Google  might not always use them (just as Google does with their regular search  results). Your best chance of having them show is to use, close to the  beginning of your description tags, the words that you know pull up  sitelinks. Also, be as descriptive as possible within the first 5 to 7  words.
3. Meta Descriptions and Social Media Marketing
Ever  wonder why some Facebook links have great descriptions and others don't  seem to make any sense? It's because some site owners have taken the  time to write a summary of the article and place it into their Meta  description tag, and some have not. If your article has a Meta  description, Facebook and Google+ will default to that when you share a  link on your profile or "Page." If there's no Meta description, you'll  usually see the first sentence or so from the page being used as the  default.
While anyone can edit the description that Facebook  defaults to, most people don't. And at this time on Google+ you can't  even edit the default description. You can either leave it as is or  delete it all together. Let's face it -- most of the time the first  sentence of an article is not a good description of the rest of it. It's  not supposed to be, because that's not what a first sentence is for!
Therefore,  I strongly advise you to always write a compelling 1- or 2-sentence  description for all of your articles and blog content that may be shared  via social media, and place it into your Meta description tag. This  will give you a big jump on your competitors who haven't figured this  out yet, making your social media content much more clickable because  people will know what the article is actually about before they click  on it.
Overall, the Meta description tag gives you a little bit  more control over what people might see before they click over to your  site. The more compelling it is, the more clickthroughs you should see.  If your Meta description tags can help with that, then it's certainly  worth the few minutes of time it takes to create interesting,  keyword-rich tags that sum up what users will find when they arrive!