If you happen to share a URL to an email on facebook, usually it will generate a little thumbnail preview to go along with it.
This preview contains an image pulled from the content as well as a the title and some body text.
Say for example, you paste in a URL, press enter and then realise that some information is wrong in your post and it shows up in the preview thumbnail. You delete the post, change the information in your account, save your message then re-paste the URL back into facebook..... only to find it is still displaying the same wrong information in the thumbnail!
You can get around this, by adding :
to the end of the URL you paste into your facebook status bar. You might need to click the small X to close the current preview thumbnail, then add the ?v=1 to the URL.
This should force facebook to clear the share cache, thus showing the correct and up to date information.