The Open Graph tags are what tell Facebook what you want to display. You can configure these tags for your whole site using the Open Graph tab in the Social Configuration area, and then override the tags on each page if you want a specific title, description, or image for just that page.
As for the error, there's a few reasons this may occur. Usually, it's when Facebook can't reach your page. This can be if you have registration required to view the article or other similar things that would prevent Facebook from seeing it.
You can use the Facebook Linter (also linked to on the Open Graph config page) to see what Facebook thinks your page looks like:
developers.facebook.com/tools/lint
If none of that helps, let us know the URL of your page and we'll try to look for something else that might be causing problems.
Error on "Like" buttons in articles
