That link is this years tickets, they go on sale tomorrow (15th), I have always bought e-tickets from that site and printed them off myself.
Different sections are closed off, standing is from 1st bend round to 3rd bend and you can obviously walk anywhere round there, there is seating on 4th bend and 1st bend and of course the main grandstand on the home straight, we've always had standing tickets but I guess if you bought a seating ticket then you might be be allowed into the standing section aswell.