Silicon Valley still rules the wired world, but Boston and Salt Lake City made huge strides in a recent survey of America’s most Internet-savvy cities by Yahoo! Internet Life magazine. Boston jumped 12 places to No. 4 on this year’s list, published in the magazine’s May issue. Salt Lake City jumped 23 places to sixth, though the magazine said it could be a one-time spike caused by the recent Winter Olympics. San Francisco; San Jose, California; and Austin, Texas, maintained their grip on the top three spots, which they’ve held in all but one of the five surveys. Don Willmott, the magazine’s technology editor, said the magazine uses a formula that measures more than just Internet use and high-tech jobs to get a sense of which communities make the most of the Web. Willmott said analysis includes basic statistics, the extent to which businesses are online and the sophistication of the users. “We measure that by how often they shop and how many have gotten fast access,” he said.