To navigate the site, use the top menu above. The drop down menu will take you to lists or articles. Above the list of articles there is a box called "title filter". If you are in the chest section of cases and articles and want to see all the articles with collapse in them, just type "collapse" without the quotes into the box and press enter. If you want to see all the articles under one category choose all from the drop down menu labeled Display# (you can see this when you are on a page which lists articles e.g. Cases and articles>Chest).
Above the title is a set of links called "breadcrumbs" and labeled "You are here". As you navigate further into the site, this will provide links back to the section you are in (not the same as the back button on your browser).
Use the search box to the top and right of the site is you want to find something specific e.g. appendicitis.