How to optimize site content for inserting in social media WYSIWYG-editor?
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When we paste a link to some site in WYSIWYG-editors of social networks, sometimes we see a preview of the site. Like:

  https://dl.dropbox.com/u/22619948/screenshot.png

How to optimize layout of my sites or something else in the code to force this editors to take a preview?

I only need for some references to the articles or csomething where I can start.
Or just the title of technology to google it :)

will be really thankful for help :)

p.s. sorry for link. Can't paste image because I new here :)