CSS doesn’t use HTML’s entities; it uses its own unicode escape sequences.
You need to use \00a9 for the copyright symbol.
body:after {
content:"\00a9 me";
}
See here for a cheat-sheet table which shows just about every entity/unicode string you’d ever need: http://www.evotech.net/blog/2007/04/named-html-entities-in-numeric-order/