As per documentation, the method get_the_author_meta() has a $field argument with the following possible values: admin_color aim comment_shortcuts description display_name first_name ID jabber last_name nickname plugins_last_view plugins_per_page rich_editing syntax_highlighting user_activation_key user_description user_email user_firstname user_lastname user_level user_login user_nicename user_pass user_registered user_status user_url yim I wonder, what is the difference between last_name and user_lastname (first_name and user_firstname respectively ). Which property am I supposed to use and what ...