1. A method for performing error checking on a structured document, comprising: performing by a first thread executing on at least one of one or more processors that are capable of performing multi-threaded executions: identifying one or more new elements in the document; assigning an identifier (ID) to each new element; and storing a copy of each new element in a first queue, the copy of each new element including the ID associated with the new element and at least one of text and structural information associated with the new element; and performing by a second thread executing on the at least one of the one or more processors: retrieving each copy of each new element from the first queue; applying error checking to each retrieved copy of each new element to detect errors associated therewith; and in response to detecting an error associated with a retrieved copy of a respective new element, generating an error checking result comprising at least the ID associated with the retrieved copy of the respective new element.
9. The method of claim 1 , wherein the applying error checking to each retrieved copy of each new element comprises: applying the error checking to a retrieved copy of a new element responsive to determining that an element currently exists within the document that has an ID that is the same as the ID associated with the retrieved copy of the new element.