The OpenSkills systems make exclusive use of HTML for system user interfaces. This is so that systems may be accessed by any member regardless of their location or choice of operating system.
All OpenSkills HTML UIs must conform to the W3C specifications, and more specifically, validate using the W3C Validator.
See the CSS page for the core stuff.
Web Scripting means:
The OpenSkills systems use CSS and EcmaScript to implement a number of looks. This is nicely demonstrated by the CSS Zen garden site.