Sometimes, you want category navigation to be present on every page of a site. This is often done as a menu of categories on the left side of each page where the current category is highlighted. WSN includes an option for that which you can activate at Admin Panel -> Settings -> Switches -> "Left side category tree menu". Note that this category tree only expands the first two levels of categories, if you have third level subcategories people will need to reach them the usual way.

To edit the look of the left side category tree menu, go to Admin Panel -> Themes -> Manage Templates -> "Stylesheet". You can style .leftmenuleft to style the table column that has the menu and .leftmenuright for the column that has the page content. .categoryleftmenu is a wrapper around the full menu. The menu items are an ordered list with <ul class="catmenu"> for each group of subcategories (and the main group of top level categories) and <li class="catmenulinks" for each individual category or subcategory.