All my websites share one thing in common: standards. Standards play an increasingly important role in a quality website. It's easy to envision a design, create it in whatever way possible, and brush aside the XHTML standard. Think about it: would you buy a house built with questionable materials? Just like you would demand first-class components from the builders, you should require compliant code.
Here at SGA Websites, everything follows the specifications set by the W3. My sites contain 100% valid XHTML 1.0 Strict code; no exceptions. The same applies to CSS and all other technologies used. To help emphasize this point, you can find valid badges at the bottom of every site made by SGA Websites. Feel free to click them to verify the code.
Keep in mind that, although the sites are delivered with valid code and CSS, if the owner decides to alter the HTML content, it's impossible to ensure that the code remains valid, unless they share the same philosophy that I do.
Remember, it's more important to do what's right than what's easy. Even if it takes a lot more time; having a standards compliant website shows a level of professionalism that will be appreciated.