[citricsquid]

CSS and HTML and compatibility has nothing to do with UI design. Someone who does CSS and HTML would be a "frontend developer", a "ui designer" is someone who designs. The roles can be combined, but if you were to say "I am a UI Designer" that wouldn't mean you deal with CSS and HTML.

[bluetshirt]

Arguably, until traditional software developers are able to grok these distinctions, you're not going to see many of them "crossing over" to design work.