You can navigate around this website in a number of different ways, which are designed to imitate the process you might go through when writing an essay.
You can just click on the blue underlined text. Each page of text indicates all the other text pages on the site which link to it, in the "parent nodes" section at the top of the screen, so you can quickly see what the related pages are for any topic.
Many text pages have an associated mindmap, which is indicated by a small picture in the top right hand corner of the screen - click on this picture to bring up the mindmap. Circular or elliptical areas on the mindmap are linked to other mindmaps, which you can use as a way of getting an overview of the site. When you want to see the text page that goes with the particular mindmap you're viewing, click on the picture of a notepad in the bottom left corner of the mindmap.
You can also click on the tree menu on the left hand side of the screen, which gives you an outline view of some of the main topics on the site.
Unfortunately, this version of the site only works properly with Internet Explorer.