Facebook Thumbnail Image for Links
Question:
Facebook displays not the correct or a random image when I paste a link to my website on a Facebook Wall.
How can I choose the image that Facebook displays?

Answer:
Facebook will pick the first image it can find on your website. This is often times a sidebar image which you may not want.
Follow these steps to specify an image that Facebook will use:
1) Log into WordPress
2) Go to “Media” -> “Add New Media” and upload an image
3) Copy the Image URL
4) Go to “Appearance” -> “Editor”
5) Select the “Header”(header.php) file from the file list on the right.
6) Add the following below the opening header tag:

Note: The changes are not instant! Facebook will needs to re-crawl your site.
The format is called “Open Graph” – You can learn more directly at Facebook [Link]
