记住HTML文档上的最后滚动位置以便重用

I have something called "Course Reader". It is a big HTML document that can contain text, images, youtube videos, soundcloud audio and so on. Most of the stuff is imported from external sources like EPUB documents, so I don't have much control of the HTML and how it's is generated. I need to create the ability to remember the last position on the document where the user was, so when the next time the document is loaded (maybe it won't be the same browser or the same device), I can take the user to that position.I have something called "Course Reader". It is