Use wp_enqueue_scripts, not wp_print_styles, to enqueue scripts and styles for the frontend
If you are enqueueing scripts and styles, you will want to use one of these three hooks:
- wp_enqueue_scripts (for the frontend)
- login_enqueue_scripts (for the login screen)
- admin_enqueue_scripts (for the admin dashboard)
Don’t let the names fool you — they are for both scripts and styles. We’ll probably add equivalent *_enqueue_styles hooks in 3.4 just to make it more obvious, but these hooks have all existed for some time now.
A possible incompatibility with WordPress 3.3 could arise if you are using the wp_print_styles hook to enqueue styles — your styles may end up in the admin.
The fix: Use wp_enqueue_scripts instead. Yes, it’s that easy.
Edit: Yes, the same goes for registering styles. Registering or enqueueing (styles or scripts) should occur on *_enqueue_scripts.