Why web standards should be important to clients
I wrote this post a while back. The content can still be relevant but the information I've linked to may not be available.
There's a nice summary of the benefits of web standards in an article called Tell your clients why web standards should matter to them on the That Web Guy Blog. Really, the points here are well-known and building websites using web standards is pretty much a no-brainer in my opinion. Nevertheless, there are many websites and web designers/developers out there who 'don't get it'. Perhaps the above article will convince a few more of them.
PS: There are some other good articles on the That Web Guy Blog. Nice design and layout as well!