Agreed, you would never sell "CSS" to a client...Rather, you might state that you can turn around projects much faster than your competitors because of your vast experience, as well as your skills in employing some advanced technology...blablabla. You could also add that your use of this mysterious advanced technology allows for web pages to be "lighter", hence faster for their customers to view, and accessible to users with disabilities, which also helps with search engines reading/indexing their website, etc. So, yeah, would never sell "CSS" directly. ;-)
The same can be said with automobiles - customers don't care what is under the bonnet. Except that this is not true, customers do care even if it is just a plastic engine cover that they see.
So the challenge is to market one's CSS as a quality product rather than the naive CSS that most websites use. So it is a 'Mercedes' rather than 'GM' product, a Swiss watch rather than a badge engineered generic Chinese watch, a fine meal rather than a bag of fast food.
The reality of most websites is that they are throwaway, within a couple of years it will look tired. If this premium website product can last longer without having a refurbishment then that can make a difference to a business that cares about more than the next quarter.
