The Bayer pattern is the most common sensor arrangement, this article has a little information on it:
http://www.dpreview.com/news/0706/07...akhighsens.asp
I found this webpage on Irfanview and RAW files by the way, you might want to have a look:
http://en.irfanview-forum.de/viewtopic.php?=&p=4415