wp_enqueue_script warning

Notice: wp_enqueue_script was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks. Please see Debugging in WordPress for more information. (This message was added in version 3.3.)

This PHP notice warning appears if WP_DEBUG has been set to true. It will have been caused by a theme or plugin where a script has not been correctly enqueued. WordPress Codex page WP_ENQUEUE_SCRIPT gives examples of how it should be used.