Initially, the Department for Transport (DfT) proposed to create the HS2 in two phases: Phase 1 being from London to the West Midlands (including Birmingham) and Phase 2 taking the line further North. In 2015, Phase 2 was split into two stages: Phase 2a will be from the West Midlands to Crewe. And Phase 2b will have two legs: one from Crewe to Manchester and the other from the West Midlands to Leeds and South Yorkshire.
The map on the right uses magenta for Phase 1, yellow for Phase 2a, red for Phase 2b.

As explained on this web page, there are currently two possible routes for Phase 2b. There's the consultation route (2013) and the preferred route (2016). Because the Department for Transport (DfT) provides separate data files for these two routes, this web site now has separate web pages for the two routes.

You tried to access the web page at
http://www.thehs2.com/phase2b/kmls/
You may wish to try this link for the preferred route or this link for the consultation route.

Or you can access the separate web pages for two routes for Phase 2b using the menu on the left.