I actually did
a very similar topic a few weeks ago. Instead of just the Internet, my challenge was for geek culture in general to be dominated by women. One of the replies there suggested that the reason men took over IT and geekdom was because Asperger's Syndrome, which often hurts social skills, affects far more men than women, but I feel that this alone doesn't come close to explaining the size of the disparity. There is a non-negligible amount of girls with Asperger's, and not all people with Asperger's are attracted to geeky endeavors -- some, for example, are more artistically-inclined. Plus, how much of the prevalence of Asperger's has to do with the fact that everyone and their dog is being diagnosed with it nowadays, thanks to pushy parents who want an explanation as to why little Johnny isn't making friends like he "should"? But I'm going way off-topic. The main reason for the male dominance of the Internet, I feel, is similar to mowque's explanation: the Internet was developed by the military.
A solution that I feel would work better than emphasizing the Internet's communicative abilities (which only came into their own in the '90s, by which time IT was already dominated by men) would be to go back to the feminist movement in the '50s and '60s, and have them latch onto technology as a means of liberation. To rephrase what I said in my original thread, technologies like microwaves and vacuum cleaners, as well as institutions like public schools and day care, have all reduced the domestic workload of women, allowing them to pursue jobs outside the home. Plus, IT and science-oriented fields are places where the traditional advantage of men -- physical strength -- no longer applies, creating an even playing field between the sexes. Someone like Gloria Steinem could take a look at this and realize, "You know, technology has done so much good for women. Shouldn't we be supporting science education for our daughters?" Even though nobody back then saw the computer revolution coming, an increased focus on getting young women interested in science will mean that a lot more of them will be headed for computer-related fields than in OTL. You may not see a female-dominated Internet in this case, but it will be a more egalitarian one.