<li class="wp-has-submenu wp-has-current-submenu wp-menu-open menu-top menu-
 icon-a" id="menu-posts-a">

function admin_scripts_advertiser_info($hook){

 if ('menu-posts-a' != $hook ){
return;
}

wp_register_style( 'admin_advertise',get_template_directory_uri().'/css/admin.advertiser.css', array(), '1.0.0', 'all' );
wp_enqueue_style( 'admin_advertise');
}
add_action( 'admin_enqueue_scripts','admin_scripts_advertiser_info' );