Why do these characters - Â Ã Â - that were not added appear on Event registration pages created using CKEditor?
That type of thing is normally character encoding problems. The first thing I'd check is what the character encoding on your database tables are, e.g.

SHOW CREATE TABLE civicrm_event;


If it says charset=latin1 or anything instead of utf-8 at the bottom then I'd guess that's your problem. You can see here for ways to fix it: https://stackoverflow.com/questions/2150256/how-to-change-all-the-tables-in-my-database-to-utf8-character-set

Edit: To save anyone reading all the comments, in this particular case it has something to do with ckeditor and character encoding. Workaround is use a different browser like firefox.