The inner geek in me really loves this collection of nerdy street art; the error message is nothing short of brilliant.
Through pieces such as this, even non-geeks get to learn the basics of HTML coding. Unsurprisingly, there is even a web site that collects together the finest examples of geek graffiti around. This stuff is brilliant -- even the name rules.
Sources: Wooster Collective |Life Lounge | Popfi | Loveable Rascal | Flickr