Minimum acceptable XHTML markup standards

Not all Web content markup s equal even if all of them may be structurally valid code.

Web Designers and developers that are used-to creating all their layout markup using tables may find it difficult to understand how to use CSS for layout although they may very well understand the virtually limitless number of reasons to use CSS layout. For a converted/'born-again' developer using CSS layout, it unbearable to see how may consultants and Web Design agencies out there are still using tables for layout and fleecing their customers for what looks good on the surface, but is low on usability, future compatibility, and is just quick machine-coding to make a quick buck - Do they expect to make repeat customers once the customers find out that they are not getting cutting-edge services?