If the client wants backwards compatibility, then it should be a billable extra. If you're billing on an hourly rate, it's in their best interest to get the pro

If the client wants backwards compatibility, then it should be a billable extra. If you're billing on an hourly rate, it's in their best interest to get the project finished as fast as possible. I don't think the document was anti-backwards compatibility, just well, you know clients... they are always wanting the look like a Porsche, while still driving a rusty old pick-up. They are just trying to justify the lack of support in an easy to swallow way. You want support, expect to pay for it, but realize that the money you're paying will only benefit a small percentage of your audience (you included). Everyone's had (and still get) those clients using IE5, saying that if it doesn't work for them, it won't work for the rest of the internet.