The story starts as always with the user, yes! … that villain, let’s suppose that he has committed the inexcusable crime of clicking the submit button of a form. The poor browser that struggles to keep opened the 100 tabs without crashing begs the operating system to open a magic portal known by some scholars as TCP connection. At the gates o internet he meets the omniscient wizard of DNS that indicated the path to the castle where the WebServer reside. It wanders form router to router and hub to hub and almost when he lose the hope and his TTL finally he found the castle. Here the WebServer listen his web request and consults the infallible code of his sanctity THE Programmer. After thousand CPU cycles and couples of OS interrupts the webrequest is found as nonconforming with the teaching of code so an error is handed as response. Tired and with broken spirit the the browser displays the error to his master the user.