Do I need to include citations when writing my own lecture notes, if I make them public? I am a graduate student in mathematics, writing my own notes in my spare time on a topic I'm interested in. I find it helps me understand things if I write things out in the style of lecture notes (although to be clear I haven't taken a course in this topic). These notes consist of information from a huge variety of sources, including books, math.stackexchange, wikipedia etc. and since it is for my personal understanding I haven't been citing anything. 

There is a chance, however, that I would like to upload these notes on my webpage for anyone who may find them useful. Is it acceptable to only include a paragraph at the beginning saying that none of the following is my own work, written purely for personal benefit and taken from a variety of sources, without citing anything specifically? Obviously there is a huge difference here to plagiarising work that would be considered for publication somewhere 'official', but would it still be considered unacceptable practice? 

Thanks in advance.
First, I think we should maintain good standards of ethics and scholarship for all public/published documents, regardless of whether they've been through peer-review.

Thus, even for "standard" material that's visible in many textbooks, it is "fair play" to acknowledge what you looked at to inform yourself. Indeed, this bit of information does also impart something useful to potential readers.

So, at the least, I'd have a bibliography, and, if not constantly citing those sources, at least some bibliographic notes explaining in some further detail how you used them. This could be a part of an introduction, for that matter, rather than putting it at the end.

(While it is certainly true that at some point(s) one can no longer remember where one first saw something-or-other, so it's difficult to give accurate credit, it is still possible to do a bit of historical research to find out something of the origins of an idea...)