Travelers using Denver International Airport’s free Wi-Fi service cannot visit Internet sites that airport officials consider provocative. A report in The Denver Post says the airport is blocking Vanity Fair magazine’s website, the hipster site boingboing.net and others.Airport spokesman Chuck Cannon says officials decided to block access to potentially racy sites when the airport made its wireless internet service free in November. Cannon says the airport would rather deal with infrequent complaints about access than handle angry parents whose children might see pornography.