Don't Make Bungie Kick Your Ass
The site isn't loading for us here at R.net headquarters at the moment, but it's been mentioned both at HBO and now at TeamXbox that the Halo manual includes a reference to the following URL: http://www.seventhcolumn.org.
We haven't seen it yet, but apparently that URL was displaying a numeral 7 and Don't make us kick your ass in Latin (NON FACETE NOBIS CALCITRARE VESTRVM PERINÆVM).