* A basic dropdown set of styles for WP wp_nav_menu() / wp_pages_list()
* This dropin group of rulesets uses a top level selector nav#site-main which needs to be changed to suit or added to markup.
* There is a simple series of CSS Transitions to provide a little smoothness to the opening / closing of the menu and opacity * transitioned on the li elements.
* There are background colours added and obviously these are subjective and won't suit all themes so need changing
* There is a comlimentary JS snippet that just adds classes to hovered li elements and their parents, this is named in time * honoured manner as 'sfhover' it's real purpose used to be to provide support for IE but are also useful to provide xpath * navigation back up the li nodes and used here to add li backgrounds on all hovered elements parents. In addition the script * Adds a class 'has-child' to li elements having nested ul li children.