As Bart says in his answer - the online documentation is currently experiencing problems.
I would suggest for your future installations / upgrades you prepare in the event that online material isn't available beforehand.
Note that the second you print something / save it offline it has the potential of becoming out-of-date... but it does have the advantage of serving as a true representation of exactly what was done to complete the install.
A process I've used in the past when the client reported that online comms could be problematic was
- Get an offline copy of the latest online version
- although this may seem cumbersome to print pages as PDF and collate them myself it will serve the purpose of ensuring you're familiar with the process as you've gone through it 'for practice'
- Annotate the document with known details (machine names) etc.
- this will serve also as a prompt to ensure you've access to specific information you may require beforehand (such as user credentials etc.)
- Have a final read through the documentation before storing in with your laptop
- no matter how many installations you do, it's prudent to have a note handy as a quick reminder for those oft-forgot or more technical elements of an install, the more prepared you are the more professional you will be
In the event you have the online version available I'd still use that but then I've the printed version to make annotations on should I need to go back and check something later etc.