The Like Box is a variant of the embeddable Like Button that allows you to Like a page from other sites. The embed would also show off some of the other people who liked a given Page. Facebook suggests you to instead use the newer Page Plugin, which functions similarly, but looks a little cleaner visually and is able to pull in content feeds from your Facebook Page if you want.
If you want to add the new page plugin, you can visit the FB plugin page here. Users will have to remove the old code to enable the newer plug-in and add in the Graph API.
