As it is most popular Facebook has received most questions, here is the summery of all the answers:
Use this tool to clear Facebook cache of your site (it is possible that you are not getting fresh data but old Facebook cache):
developers.facebook.com/tools/debug
If you're having trouble with your Facebook images use this tool to check for errors.
For best sharing results I recommend this plugin (Phoca Open Graph Plugin) which will add correct meta tags to your HTML document as required by popular social networks.
For correct Facebook language codes see this link: https://developers.facebook.com/docs/accountkit/languages/
Make sure you've got images big enough for Facebook to pick up:
Facebook does not like small resolution images because they are bad user experience. Use images that are at least 1200 x 630 pixels for the best display on high resolution devices. At the minimum, you should use images that are 600 x 315 pixels to display link page posts with larger images.
If your image is smaller than 600 x 315 px, it will still display in the link page post, but the size will be much smaller.
Check here for Facebook's best sharing practices
Facebook has a set of open-graph meta tags that it looks at to decide which image to show.
The keys one for the Facebook image are:
<meta property="og:image" content=" ia.media-imdb.com/rock.jpg"/ >
<meta property="og:image:secure_url" content=" secure.example.com/ogp.jpg " />
and it should be present inside the <head></head> tag at the top of your page.
If these tags are not present, it will look for their older method of specifying an image: <link rel="image_src" href="/myimage.jpg"/>. If neither are present, Facebook will look at the content of your page and choose images from your page that meet its share image criteria: Image must be at least 50px by 50px, have a maximum aspect ratio of 3:1, and in PNG, JPEG or GIF format.
Yes, you just need to add multiple image meta tags in the order you want them to appear in. The user will then be presented with an image selector dialog: Facebook Image Selector
Once a url has been shared, Facebook's crawler, which has a user agent of facebookexternalhit/1.1 (+https://www.facebook.com/externalhit_uatext.php), will access your page and cache the meta information. To force Facebook servers to clear the cache, use the Facebook Url Debugger / Linter Tool that they launched in June 2010 to refresh the cache and troubleshoot any meta tag issues on your page.
Also, the images on the page must be publicly accessible to the Facebook crawler. You should specify absolute url's like example.com/yourimage.jpg instead of just /yourimage.jpg.
No. Much like search engine crawlers, the Facebook scraper does not execute scripts so whatever meta tags are present when the page is downloaded are the meta tags that are used for image selection.
You can add the necessary Facebook namespaces to your tag and your page should then pass validation:
<html xmlns="www.w3.org/1999/xhtml" xmlns:og="ogp.me/ns#" xmlns:fb="www.facebook.com/2008/fbml">
original post: stackoverflow.com/a/7623986
You might want to try to disable any sort of compression, for example GZIP compression in PHP. This helped me with a similar problem in a Joomla 3.3 website.
I had GZIP compression enabled and Facebook was unable to scrape my website. Disabling the GZIP compression solved that issue.
I have not figured out yet if it's a Joomla problem or a GZIP/PHP problem in general or a facebook scrape problem.
original post: stackoverflow.com/a/26016151