HTML PARSING

The input to the HTML parsing process consists of a stream of code points, which are then passed through a tokenization stage followed by a tree construction stage to produce a Document object as an output. Mostly, the data handled by the tokenization stage comes from the network, but it can also come from a script running in the user agent, e.g. using the document.write() API. The tokenizer and the tree construction stage have only one set of states, but while the tree construction stage is working with one token, the tokenizer can be resumed. Because of this tree construction stage is often considered reentrant. To handle such cases, parsers have a script nesting level, which must initially be set to 0 and a parser pause flag, which must be initialized to false. PARSE ERRORS: As mentioned earlier, while parsing a resource, it is checked with its syntax and if something doesn’t match the standard protocol it raises a Parse error. If a resource is found to be error-free it becomes a document. Parse errors only deal with errors regarding the syntax of an HTML document. In addition to checking for parse errors conformance checkers also validate documents to match the basic conformance requirements. The error handling for parse errors is well-defined. If one or more parse conditions are found within the document, it is the duty of Conformance checkers to report at least one of them and report none if no error is raised. Conformance checkers may report more than one parse error condition if more than one parse error condition is encountered in the document.