An SGML fan, an XML fan, and an HTML fan are watching a movie when they notice smoke coming out of a trashcan.
The SGML fan says “We must convince the theater management to hire an expert to write a DTD for emergency-announcements, and sell them an expensive application for archiving announcements, and get them to hire a team to convert all their old announcements to SGML!”
The XML fan says, “There’s no time for that! We must train all the audience members to recognise XML, and then start a committee to investigate the possibility of starting negotiations to form a working group to write a paper on the future evolution of emergency-announcement semantics!”
Meanwhile, the HTML fan takes out his wireless PDA and types in:
<h1><span style="color: red;">FIRE!</span></h1>
which he quickly hacks the digital projection system to display, saving the lives of everyone in the theater.
(Found on Molly.com)