Be very careful when you have encountered this because it's a scam. According to blog of Anti-virus site Sophos,
Like the "Preventing Spam / Verify my account" scam which went before it, the scammers have managed to waltz past Facebook's security to replace the standard "Share" option with a link labelled "Enable Dislike Button".
The fact that the "Enable Dislike Button" link does not appear in the main part of the message, but lower down alongside "Link" and "Comment", is likely to fool some users into believing that it is genuine.
Check out the Facebook Dislike button page scam image below.
Share and Enjoy!