Odd oversight

So, I was reading an interesting article on generating columns using absolute positioning here:
http://24ways.org/2008/absolute-columns
and I noticed something very odd. The site doesn’t appear to have been checked extensively in Firefox. If I had to guess I would say it was programmed for Internet Explorer 7, but they never bothered to carry over the transparency effects to Firefox. There are a few other differences as well, nothing that looks broken per say, but it is different enough to give the impression that the second most popular browser in the market was overlooked.
Now, I’m trying to keep the snark level to a minimum here, as many of the people who write for the site can be described as nothing less than absolute geniuses. However, it does make me wonder what sort of lessons can be learned from this. Either way the articles themselves are quite good, and I encourage people to take a look when they get a chance.