<meta name="description" content="This is an example of a meta description. This will often show up in search results.">
The meta description is normally used by search engines when making the snippet for the document on search result pages. This tag is not used when determining a page’s topic, but as it is one of the first things seen by users, it is important in influencing the clickthrough rate and gaining traffic from organic search.
Length – the displayable length of a meta description is around 165 characters, depending on the search engine. Search engines may not always show the defined meta description – for instance, if it thinks a snippet from the page will be more useful to users it will create its own snippet.
Google’s Double-description Trick
By setting a double-length meta description separated by a period, Google will show the half of the description which best matches the user’s query. This is certainly not best practice, but is useful for testing descriptions or serving relevant descriptions for multiple queries.
<meta name="description" content="This is an example of a meta double length description for Google. The first half must be close to 165 characters and end with a period (full stop) - like this. This is the start of the second meta description - either the first half, or the second half of this meta description will be displayed (this half must also be 165 char)">Next: Meta Keywords >