In the past few years I have added many long works to the Ancient Buddhist Texts website, including the Jātaka-aṭṭhakathā (547 stories), Dhammapada-aṭṭhakathā (301 stories) and the Great Chronicles of the Buddhas (222 stories).
It occurred to me that keeping track of what one had read was becoming increasingly difficult, and decided one way to help with this would be to add checkboxes, so when a page is read it could be checked off.
Once I added it to the longer documents it became clear that it could be used for smaller documents, and for index pages with lists of documents, so I have now added them in there also.
Having added it to Ancient Buddhist Texts I also have added into the Storybooks section of my Photo Dharma site, where it serves a similar purpose. Of course, when the document is short enough that no such help is required it has been omitted.
The checkbox remembers its state through local storage, and so is private. I hope this will be a useful addition to the site that will help people remember what they had read, and what is still to be read.