In the "Managing Your Users' Experience" module of the "Building Applications with Force.com - Part 1" online training course, the link in the "Resources" tab didn't work for me using the Firefox browser on Windows 10. When I clicked the link to open the PDF file "Managing Your Users' Experience Exercise Guide", I was taken to the following page which showed a 404 error for file not found:
Looking at the name of the PDF file, I figured that the file name has an apostrophe in it that was causing the problem, so I looked up the URL encoding for the single apostrophe and found it to be %27. So I added %27experienceexerciseguide.pdf to the URL to produce the following URL which enabled me to open the PDF file:
If you are getting the same error for the same PDF file but the link above doesn't work for you, try adding %27experienceexerciseguide.pdf to the URL you get after clicking the link for the PDF file.