Where do I find X11 compatible with OS X 10.8.2?

Welcome to the Apple Support Communities

X11 isn't preinstalled by default in OS X Mountain Lion. To install it, open Utilities folder, inside Applications folder, and open X11, so your computer will ask you to download it. If you don't find it, go to this site to install X11 in Mountain Lion > http://xquartz.macosforge.org/landing/

NOTE.

The App launch and download request take you here http://support.apple.com/kb/HT5293

Which then has a link similar to mende1's link (minus the /landing bit)

9:37 PM Tuesday; March 5, 2013

Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"

 iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously

The link available in that Apple support article just redirects to the /landing page, so it's the same website

I should have been clearer about that, as I knew the site was the same one.

EDIT

@e_hutchinson

For the Points

9:48 PM Tuesday; March 5, 2013

Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"

 iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously

Message was edited by: Ralph Johns (UK)