Nope, that link not working either. Network Rail must have its website set up so that you can't link directly to individual pages. (Any conspiracy theorists like to offer an opinion on why that might be?!).

So:
- go to http://www.google.com
- click on advanced search
- in the first search box type 'Southern supplemental'
- in the site or domain box type 'networkrail.co.uk'
- press Enter
- click on the first result and voila!

Or:
- go to http://www.networkrail.co.uk
- click on 'For Business' tab at the top of the page
- on the left hand menu click on 'Track Access' (second up from the bottom)
- click on '2. Completed Consultations'
- find '2009.09.08 New Southern Railway 36th Supplemental - Consultation closed 18 September 2009' (scroll down to the bottom and work your way up)
- and there you are.

What not to do:
- use Network Rail's search facility to look for 'Southern Railway 36th Supplemental' (or variations thereof) cos you won't find it.