I'm a designer myself and I don't consider myself a "technical" founder (though I will use the term "semi-technical". I feel that in order to be considered a technical founder, you should have mastery of programming and servers and all those super-technical details — HTML/CSS/Design don't cut it.
If the definition of technical (in the context of web/tech startups) means knowing how to program, then I guess any designer who can program is technical.