Error 404

[itisraffycame]

I’ve used the web version and the python manual version, but I always end up with the same errors.
On the web version I get stuck to “downloading pages...”, while on python I only get “error 404: not found”. What do I do wrong? What can I do?
Because of the pandemic, I’ll need to have my books in PDFs on my device and I have no clue about how to make this work. Can someone tell me where I’ve made a mistake?