> Otherwise, it's an IE-specific "feature" that does not adhere to web standards.

Oh, I am sure it is. Alas IE sets the standards now and w3c is pretty much irrelevant. You either play along or get left behind.

Edit: That came out a bit strong. Let me elaborate. The fact is that most pages on the Internet are made for and tested with IE, since it is the leader by far. For most pages that is not a problem, but for a certain percentage that will make Firefox fail to render it as intended. If the people at Mozilla want to make their browser usuable on as many pages as IE is, they need to support those extensions. But it appears they would rather make a statement by ignoring them, which is their loss, because most people will not even understand why it doesn't work right, they will just see that it doesn't. And that will ensure that Firefox never gets anywhere.