1. An automatic method of indicating changes in a structured document implemented via a computer, the method comprising: determining that a unit of content in an updated version of a structured document and a related unit of content in a previous version of the structured documents are associated with the same entry, wherein determining comprises: accessing a base topic set having a single topic identifier associated with each unit of content in the previous version of the structured document; accessing an undated topic set having a single topic identifier associated with each unit of content in the updated version of the structured document; identifying a particular topic identifier in the updated topic set that corresponds to the same particular topic identifier in the base topic set comparing the unit of content associated with the particular topic identifier in the updated version of the structured document with the related unit of content associated with the particular topic identifier in the previous version of the structured document to determine whether the unit of content in the updated version of the structure document has been modified with respect to the related unit of content in the previous version of the structure document; generating a table of contents associated with the updated version of the structured document, the table of contents having one entry associated with each unit of content in the updated version of the structured document; and marking a first entry in the table of contents if the unit of content associated with the first entry has been modified a predetermined degree from a previous version of the content, wherein the predetermined degree is represented by a difference metric as determined by a content comparator, such that: in an event that the difference is counted as a modification, the difference metric represents each change in words, tags, and formatting, wherein the changes comprise changes in font, color, size, inserted content, and deleted content between the respective units of content in the updated version of the structured document and the previous version of the structured document; and in an event that not all differences are counted as modifications, changes are classified by type such that changes of meaning are classified in a different type than changes in form, wherein changes in form include rephrasing that does not change the meaning of the content, and the difference metric represents the number of changes of meaning within each unit of content.