CSS Web Site Planning Today
The vast majority of the effort and project planning on large-scale Web projects today trivializes the UI layer and treats it as an afterthought, when in fact it can deeply impact content management, Web applications, search engine optimization (SEO), bandwidth costs, site performance, and maintenance efforts. Plans typically start with the back-end software and only touch on the UI in terms of design.
Fortunately, there are ways to pare down the long-term risks and remove the constraints of traditional Web coding. Embracing modern techniques starts with the W3C and its recommendations, often called Web standards.
The issue should be considered not only in terms of your design, but also where the content management, applications, and other dynamic systems are concerned. If a Web site is to reap the benefits of a Web standards-based UI, it needs to be considered at all levels, and plans should be introduced that will allow the site to grow intelligently.