You might want to look in to git (the version control system which runs github among other things). That will keep changes to a file (html being only one of many) and let you roll back to a previous version reasonably easily. It sounds like it may do what you need. Although I’m finding it a bit difficult to learn, that may just be because I’m old 
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It certainly is. I’m trying to learn development to make sure it keeps going (as development has currently pretty much stopped) and thus need to learn how git works. If you have questions we are happy to answer.
Peter