We made some changes when migrating the site from one AWS account to another, and this resulted in some ill-configured images in various parts of the site. We have fixed the problem. You may need to clear browser cache to fix the issue.
Do not remove the center axle nut. That is only remove if you're doing an axle or a bearing. After the caliper is off and the bracket as well, spray wd40 or other penetrating oil, around the axle nut ring (the flange the rotor slides onto). Rust builds up over time and makes it stick to itself. Just get a mallet next and give it a "tap" from the back side on the face of the rotor. It'll pop off.