At a bus stop in Seattle, in blue chalk on the sidewalk, is a mysterious scribble: email@example.com. The cursive e-mail address is underlined in blue - a signal to passersby that they can use their cellphones to text message the address and receive a response. It is like hyperlinked text on the Internet, only here a phone, not a mouse, can "click" on it.
Graffiti artists are said to "tag" buildings, and practitioners of high-tech graffiti tag their e-mail address in blue underlined writing or on a distinctive yellow arrow to indicate their presence.
What people see when they type in the address posted on the wall or sidewalk ranges from the artistic - haiku and photography - to the practical - travel recommendations and advertisements. It's like a hidden code that links a person with others who have passed that way.
Graffiti, though illegal and considered a nuisance by cities, nonetheless remains a feature of urban life. In some quarters, tagging is viewed as a form of expression in the hands of artists. Grafedia - hyperlinked text on real surfaces - follows the same urban grass-roots traditions, though it may yet be co-opted by commercial interests as an advertising vehicle.
Grafedia has become more popular than its creator imagined when he launched the project six months ago.
"With Grafedia, I saw that the Web was going away from people's laptops and computers and more toward being ubiquitous," says Grafedia founder John Geraci, a graduate student in interactive telecommunications at New York University. "I wanted to do something that was an extreme version of that model, where you did away entirely with the idea of laptops and computers and sort of set the Web free to run through the streets."