In some academic disciplines, footnotes and endnotes are not only used for references, but also to contain elaborations or explanations of points made in the main text.
This is normally where you would insert the author and date if you were using the 'author, date' system described above. The worst case is deliberate plagiarism for whatever reason. Referencing web pages The internet is increasingly used as a source of information and it is just as important to reference internet sources as it is to reference printed sources.
Some styles put a comma between the two, others just a space: Franklin Journal articles are cited in a way that is quite similar to chapters in a book. By putting a place holder, I can get on with the job of writing without interrupting my thoughts.