Kerb your enthusiasm: the world beneath our feet

Seriously, how hard can it be? You're a workman. You I need to climb into your manhole, so you remove the cover. When you are finished doing whatever it is people do in manholes (conducting vital repair work? hiding? fighting crime?), you emerge blinking into the daylight. You replace your painted or paved manhole cover so that it matches up with the rest of the street. You move on.

But this simple task has proved too much for some. And, for the past year, Tim Pitman has, along with a team of contributing amateur photographers, chronicled some glaring street aberrations on the website. Double yellow lines perpendicular to the kerb. Box junctions thrown into disarray by an off-putting splodge of paint. For Britain's legions of OCD sufferers, they are a living hell to look at.

"In the past year, I've photographed almost 100 of these things," says Pitman, a London architect. "I see them everywhere. It's not just in London. I recently went to St Etienne and Lyon, where I found the same thing. What I've started to wonder is whether they can be accidental or not."

He has a point. It's hard to imagine how someone can look at these marks and feel that they have completed their duties satisfactorily. Moreover, the mistakes are too common to be put down to ineptitude. So what are these urban punctuation marks? Blips in the matrix, or proof of a subversive movement - underground in every sense - railing at the ubiquity of road signs and authoritarian instructions on our streets?

Sean Gabb of the Libertarian Alliance has his own theory.

"Everyone cheats at work," he says. "In the more fortunate professions, that might take the form of padding an expense account. But for some workers, there are very few chances for actual enrichment. What you can do is enrich your time. So these anomalies on the streets, which seem at first glance to be casual mistakes, are actually small acts of rebellion an enriching experience."