Good read on design implementation: The Nine Principles Of Design Implementation
The document is written semantically and logically, with or without styles.
The least amount of markup and assets are used to achieve the design.
Rules for common values are stored and used liberally.
Base elements are separated from a specific context and form a core framework.
Common elements are logically broken into reusable parts.
Customizations to base elements are available through optional parameters.
The code is easily extended and anticipates enhancements in the future.
All elements are described for others to use and extend.
The final output is an appropriate representation of the intended design.