I know people that still use really old computers. If you're trying to sell something to them, they aren't your market. If you think they care that your website looks like absolute crap on their computer, they don't really care. These aren't people that generally look at computing as anything more than something they grudgingly were forced to do. They know their computer is old and expect things not to work on them. It fits into their perception of computers being useless anyway.