Facebook comments are the most common way to communicate on the site. You can initiate a new comment on someone's wall or provide a remark to something another user posted. Either way, the symbols on your keyboard can be used to convey emotions in your comments. Among the symbols created through the use of a regular keyboard is the heart. You can add a heart by itself or use it as a part of a larger message.
Navigate to the profile of the person you want to leave a comment for by entering her name in the search field at the top of Facebook or by clicking on her thumbnail image anywhere on the site. You can also click inside the "Write a Comment" box at the bottom of any post to comment on it.
Type a less-than sign (<) into the comment box and then a "3." The symbol will look like this: <3. Enter text either before or after the symbol, if you'd like.
Press the "Enter" key to post the comment. Facebook will translate your symbol into a heart in the comment.