Facebook’s guide to sharing details some meta tags to make that sharing work better:
In order to make sure that the preview is always correctly populated, you should add the tags shown below to your html. An example news story could have the following:<meta name="title" content="Smith hails 'unique' Wable legacy" /> <meta name="description" content="John Smith claims beautiful football is the main legacy of Akhil Wable's decade at the club. " /> <link rel="image_src" href="http://www.onjd.com/design05/images/PH2/WableAFC205.jpg" />
As shown, title contains the preview title, description contains the preview summary and image_src contains the preview image. Please make sure that none of the content fields contain any html markup because it will be stripped out. For consistency’s sake, please use the <meta> tag to provide text data for the preview, and the <link> tag for any source urls.
The title and summary tags are the minimum requirements for any preview, so make sure to include these two.