The EDG CSS file (EDG.css) will load from any directory (folder) along the path from a directory up to ten levels above the directory that contains this HTML file "down" to the directory that contains this HTML file. For most systems the root directory will be less than ten levels up, but a deeply-nested set of directories might make use of so many levels.
Any copy of EDG.css that is loaded later (such as one in the same directory as this HTML file) will be able to override CSS instructions from any copies of EDG.css that were loaded earlier.
This arrangement allows a single, possibly customized, copy of EDG.css to provide CSS instructions for many HTML files (such as "/ebooks/EDG.css"), and for special customizations on a per-directory-tree basis such as "/ebooks/tech/EDG.css" and "/ebooks/fiction/EDG.css".