In terms of SEO, the Meta Description Tag is not very important to Google, has average importance to MSN, but is very important to Yahoo!.
Keep your description to 150 characters (including spaces) or less. Your focus should be in creating curiosity with the reader, but not satisfying it with your Description. If you do it right, you will achieve higher click traffic to your site. Do not repeat any keyword phrase more than three times, and do not have the same keyword phrase word repeated back-to-back.
TIP : Warning: Make sure you can back up any claims you make in your Meta Description. If you can't, you may be sued. To not allow Yahoo! to display the Title and the Description from their directory and use the ones on your website instead use:
<meta name="robots" content="NOYDIR">
Where is the description?
<TITLE>Your Site's Title Here</TITLE>
<META NAME="description" CONTENT="Your Site's Description Here">
Is your Title and Description compelling?
Does it solve a problem?
Does it suggest that it solves that problem quickly?
If you answered "no" to any of the above, you need to do a rewrite. Remember when a search is performed on a search engine, two elements are displayed in the results list - the site's Title and the Meta Description.
Heading Tags - There are six types of headings: <h1>, <h2>, <h3>, <h4>, <h5>, and <h6>. They also rank in the same order for importance, so <h1> is the most important in terms of On-Page SEO.
You can use the headings to list your "headline" (h1) with its "tagline" underneath (h2).
<h1>Complete Home Security System</h1>
<h2>Self-install your home security system in One Hour or Less!</h2>
In the above example, it allows for the key phrase "home security system" to be used naturally in both headings, thus increasing the on-page optimization score for the key phrase.
IMAGES are important to your visitors / customers. They help build brand identity and improves the overall design of your site. But search engines today can't "read" your images so SEOs have been "keyword stuffing" the image ALT tags to gain better rankings. We advise against this practice.Instead, we recommend the ALT text be descriptive of the image...not a place to inject 18 kabillion keyword phrases.
ALT Text Importance - There is a major difference between indexing and importance, or what SEOs call "relevancy". Many webmasters will point to the fact that their site comes up #1 for the term "Glendale Arizona top residential and commercial real estate specialist for 2008" and state, "See, the only place that text occurs is in the ALT tag, so search engines do index it and it counts."
Okay, let's be reasonable here. What is the likelihood of someone actually typing the above search string? Besides the SEO, the person being referenced and his mother? Slim to none, right? Over the last few years we have seen a trend here at StomperLabs which shows that using ALT text for SEO purposes has diminished. The American Disabilities Act (ADA) has strict guidelines in order to be ADA compliant. I guarantee you, they do not look favorably at ALT text that has been keyword-stuffed. Have you ever witnessed a visually-impaired individual use the Web? With a device which reads aloud the contents of a Web page, the impaired individual will be inundated with "ALT Text Spam". Sometimes the reader is stuck on one graphic for more than 40 seconds reading all of the keywords that have been stuffed. That isn't a good experience for them.
According to a Google engineer, what you should do is create an ALT [text] that is relevant to the image so it gives the user a good experience, including the visually-impaired. The ALT text is indexed, but it is downgraded in the algorithm. The reason? "We see ALT text as relevant as the Keyword Meta tag," said the Google engineer. That should say it all as Google has never used the Keyword Meta tag due to its high spam rate.
What you need to do is to use ALT text in the manner in which it was designed to be used by the W3C: to describe the image. If appropriate, a keyword phrase can be used, but under no circumstances should you stuff the ALT tag with keywords. Keep it to a simple description. Basically, remember to be compliant, not just with the W3C, but also with the ADA.