
 
                The 
ProcessingInstruction interface represents a "processing 
 instruction", used in XML as a way to keep processor-specific information 
 in the text of the document.
 
 No lexical check is done on the content of a processing instruction and 
 it is therefore possible to have the character sequence 
 "?>" in the content, which is illegal a processing 
 instruction per section 2.6 of [XML 1.0]. The 
 presence of this character sequence must generate a fatal error during 
 serialization. 
 
See also the Document Object Model (DOM) Level 3 Core Specification.