Perhaps of interest: I came across this retrospective of the author of that site and how he moved it to static hosting a couple of years ago [1].

I would also say that this library covers more or less the “lower half” of solo ball juggling in terms of difficulty. With lower ball counts (say ≤ 4), there are a lot of these patterns that have complex arm movements and can be difficult to explain with words, so having such a listing with animations and step-by-step instructions is very valuable. Starting with 4 balls, there’s less and less time for moving your arms around and it is more about the sequence of heights of the throws, which are well described with just their numeric “siteswap” pattern and you can learn them just from knowing the number sequence. The site has only the most basic of those (e.g. 534) and even very common 4-ball (7531, 633) patterns are missing with hardly anything beyond that.

[1]: https://ianconvy.github.io/projects/other/libraryofjuggling/...