The situation I am describing is the one where the NFC East has played the NFC West in 2008 and 2011. Because every year your division plays an NFC div and an AFC div.
It is supposed to swap. For example, in 2007 the NFC East played the AFC East. The Cowboys went to BUF and MIA and played NE and NYJ in Dallas. Last year they played the AFC East again. This time they went to NE and NYJ and played BUF and MIA in Dallas. They rotated.
My question was why the Cowboys have played SEA at home each of the last 2 times the NFC East has played the NFC West. I noticed it with the Jets and SEA too. They went to SEA both in 2008 and this season.