It’s worth reading the whole article, which includes some very clearly explained advice, including how to sell the benefits of progressive enhancement to clients:
When working on your own, personal website projects, progressive enhancement is something you can implement without a problem. When dealing with clients, however, it can get a bit trickier. A lot of clients are still stuck on the idea that their website needs to appear exactly the same in every browser they’ve ever used. Ever.
Explain the benefits of progressive enhancement to your clients. Tell them that it’s faster and less expensive for them to have you design the site with progressive enhancement in mind, and that their visitors likely won’t care either way, as long as the content is available.
It’s worth noting that progressive enhancement is not the same thing as graceful degradation. This article from A List Apart explains it best:
Progressive enhancement focuses on the content. Note the difference: I didn’t even mention browsers.
Content is the reason we create websites to begin with. Some sites disseminate it, some collect it, some request it, some manipulate it, and some even do all of the above, but they all require it. That’s what makes progressive enhancement a more appropriate paradigm. It’s why Yahoo! swiftly adopted it and used it to create their Graded Browser Support strategy.