Sometimes you have a new description, title or thumbnail image in your website. But when you share the website URL on Facebook, it may still using the old description/ title/ image that no longer exists.
In order to clearing the Facebook sharer cache, there are few different ways like using tinyurls or modifying the URL by adding query strings. Since Facebook considers each one as different URL this might be quick way to do it.
The best and preferred way is to use Facebook Debugger tool which is formerly known as URL Linter to clear fb cache of your website. Go to below link and Type your website's or article's URL there and click debug button..
http://developers.facebook.com/tools/debug
After doing this, re-share your website's link on Facebook. You can find that Facebook sharer displaying your latest content.
Hope this helps!!
