Job search engine indeed.com combs thousands of job sites and has found that the incidence of the term "HTML5" has been increasing rapidly since the start of 2010. "HTML5" rarely appeared in adverts before this time, but a steep growth curve sprang into being very suddenly at the start of last year.
In fact, it's growing faster than any other term, trumping both "mobile app", which appears in second place, and "Android", which comes in at third. The term "iPhone" appears in eighth place.
You can search for any keyword you like on indeed.com, and see their full top ten of booming internet-related job functions.