When I specify an anchor reference to link to another document I can get it to link to another document in another folder by specifying the folder with a slash

Like this

Folder/Document.html

But I would I do it the other way around? That is I want a document within the folder to link to a document one level down in the folder. I don't know what HTML code corresponds to that

../Document.html

That did the trick, thank you

You can also use /document.html which means

site root (ie. yourdomain.com)/document.html. (Not much use in plain HTML but is useful in CSS where the page could be in any number of directorys)