The link you posted points to the ubuntu guide logo file.
Instead, just use:
The index page automatically redirects to the latest release so your link will never go out of date.
Ubuntu also has an LTS edition, the ubuntu guide for the latest one is accessed from a link at the top of the latest release guide.
This Ubuntu Guide is just that: a guide. It is very very useful for quick howtos but should not be considered "documentation" for Ubuntu. Official documentation lives at https//:help.ubuntu.org
There is a community contributed documentation page from there - which also links to the Ubuntu Guide. There is also an official wiki, where you will find the release notes