It's free to post a note on your profile or someone else's profile, and free for visitors to read your notes.
To post a note on your own profile click My Classmates® in the top portion of any page. (For mobile users, click , you may have to expand to make your selection). Click View Profile and then Notes. From there, you can write your message and click Post.
To leave a note on another member's profile, click on their name from a Class List, search results page, or elsewhere on the site. From their full profile page, click Notes, type your notes in the space provided, and click Post. Keep in mind that you cannot edit or delete your note after you submit it.
Notes you submit to someone else's profile will usually be published automatically, although the owner might have changed their settings and opted to publish them manually. If that's the case, your note won't appear until they log in and choose publish it.