Next big thing:

At least 15 percent of the top 10,000 websites are conducting A/B tests at any given time, according to BuiltWith, an Australian company that scans sites to see what types of third-party software they are using. The not-for-profit Wikimedia Foundation, which publishes Wikipedia, tested various tweaks to its fund-raising messages throughout 2013, with results a spokesman calls “amazing.” The organization says the more effective its appeals are, the fewer of them it has to show.