For those still getting their heads around Gmail, it may come as quite a shock to learn that email is now 40 years old. The now somewhat aged electronic mail system celebrates its birthday alongside web founder Tim Berners-Lee. 

Unfortunately...

Whether it's a work of graphical beauty or just a quick scrawl, graffiti is made all the better when it's got a touch of the geek. Below you'll find 33 fine examples ranging from some nice clear stencilling to some fairly obscure coding references...