In the Discworld novel Going Postal, Sir Terry, who died aged 66 on Thursday, wrote about the way that the murder of an operator of a semaphore tower, John Dearheart, was marked by his colleagues. His name was included in admin messages (known as overhead) sent around the semaphore or "clacks", network prefixed with three control characters, GNU, that kept it circulating forever. In a similar way, many net server and website administrators are adding the text "X-Clacks-Overhead: GNU Terry Pratchett" to the headers their machines share with every computer that requests web pages from them.
SimplyFixIt is proud to now send clacks.