This site is organized in the usual manner, with general topics arranged as top-level folders and more specific topics arranged as related subpages.
With google sites, authors write pages that wind up embedded in generated html. While you can still write html in these pages, including links via relative "href" paths, such links are transformed when you save the edited file so that they contain absolute "href" paths. The next time you edit the page the relative paths no longer exist. There are other related transformation issues (e.g. you also lose your own html formatting which can make it difficult to edit the next time around). This transformation process is a significant matter because, for one thing, relative paths are highly desirable for html writers like me who wish to preserve location independence in their documents. For this and other reasons I decided not to hand-convert my original html files to google pages when I established this site and instead resorted to attachments. Likewise that generally applies for subsequently added documents.
Hopefully you are using a browser that allows you to open a link to an attachment when you click on it (or a "download" link) rather than only save it (IE8 does it right but not the release of IE9 I installed - which I immediately uninstalled when I discovered that "feature" by the way - beware). If not you will need to save the attachments then browse them locally. Another and probably better option if your machine can unzip zip (compressed) files is to download, save, and unzip related _attachments.*.zip files locally (Vista can do this using Windows Explorer by right-clicking on a zip file via Extract All...). These zip files contain as a single downloadable file the other related attachments (except when an attachment is itself a zip file in which cases you download and save them separately). Then you can browse the unzipped attachments locally, which should allow for link behavior just like in days apparently gone by.