Kathryn Corrick on how the internet has returned public art to the streets

When I was at college in the mid-1990s, I knew two people who owned mobile phones (the type with long aerials). It took at least five minutes to download a page from the internet and most people still wrote their essays by hand. It was also the heyday of strange-sounding degree courses - mine was called "Art in a Community Context". While students at Goldsmiths were playing with formaldehyde and becoming media stars, we were designing installations for school playgrounds and examining recent trends in public art.

Today, virtually everyone has a mobile phone and high-speed internet access is becoming common. Only eccentric students use pen and ink to write their essays. At a time when conceptual art has been severely criticised for putting style before substance, certain artists have responded by returning to the streets.

"Warchalking" is an art form involving chalk markings drawn on urban buildings and pavements. Contrary to expectations, it is not a form of graffiti, but a movement that aims to bring the benefits of free internet access to everyone. It began in June 2002, when chalk markings first appeared on pavements in the City of London. Most of them were put there by Matt Jones, an information architect and designer of BBC News Online's first website.

The aim of the marks was to alert passers-by to the existence of Wireless Access Networks (WANs). These are office-based IT systems allowing computers to connect to the internet via a central transmitter. Instead of the office being clogged with wires, each computer has its own receiver. The computers can then receive information from the server without being physically attached to it.

The good thing about this (or perhaps the bad thing, if you're one of the companies in question) is that the signal range of a wireless network is usually around 150 metres. This means that people on the street outside can also access the internet - so long as they have a laptop equipped with the right kind of aerial. Warchalkers spend their time searching for wireless network signals and chalking their positions on the pavement for the benefit of other laptop users.

Although warchalking aims to exploit the latest technology, the movement's roots go back to the Great Depression. Then, hobos used chalk marks to convey information to other "knights of the road" about friendly houses, freshwater points, safe campsites and so on. The technique was also adopted in 1996 by the artist Heath Bunting, who would chalk website addresses inviting responses on walls around cities .

The appeal of this latest manifestation is that - in theory, at least - it enables everyone to access the internet for free. If you can find a clear signal and you have the correct equipment, you can surf the net for as long as you like - so no more need for AOL or Freeserve.

But before you purchase an aerial for your laptop and go searching for chalk marks, remember that chalk washes off in the rain, and the symbols are rarely replaced. Also, the number of companies using wireless technology in the UK is still relatively small. More important, perhaps, the movement is prompting a kickback from the corporate world. Nokia has declared warchalking "illegal", and others have labelled it a form of cyber-hacking. What's more, warchalking could be quickly superseded by another movement, Wi-Fi Zone, which aims to provide licensed public wireless connections that don't rely on accessing companies' networks. So if you want to be part of this innovative movement, you'd better start looking for the signs now.

Further details on warchalking and links to Wi-Fi can be found on the New Media Awards weblog.