Rolf Molich owns and manages DialogDesign, a small Danish usability consultancy that he founded in 1993. Rolf conceived and coordinated the Comparative Usability Evaluation studies in which more than 100 professional usability teams tested or reviewed the same applications. Rolf was a principal investigator in the Nielsen Norman Group’s large-scale usability test of 20 US e-commerce websites, involving more than 60 users. He has worked with usability since 1984 and wrote the best-selling Danish book User Friendly Computer Systems, of which roughly 30,000 copies have been sold. The book is now available in English, with the title Usable Web Design. Rolf is also the co-inventor of the heuristic evaluation method (with Jakob Nielsen). Rolf is an experienced speaker. His 24 tutorials at the Nielsen Norman Group World Tour attracted roughly 1,000 participants. The overall average participant evaluation of his tutorials was 4.46 on a five-point scale.