Look at the contents of the volume.err file after running HelpTag (where volume is the base name of your volume.htg file).
Each error listed in the volume.err file begins with a string of asterisks (*****). For example, the following error was detected at line 54 of the file actions:
***** Line 54 of actions, Missing end tag for LIST: ...the execution host becomes the current working directory. <s2 id=EverythingYouNeedToKnow> E... Current element is LIST begun on Line 28 of actions.
A few lines of the file are shown to give you some context for the error. Also, there is a hint that the current element is a LIST started on line 28 of the same file. An <s2> is not allowed within a list, so it appears that the author forgot to enter the <\list> end tag.
It's possible for a single, simple error to produce several error messages. This is because the first error may cause the parser to lose track of the intended context, making it impossible to interpret subsequent markup properly.
Most processing errors result from these common mistakes:
Omitting an end tag
Using an incorrect entity name
Referring to an invalid element ID
Omitting an end tag for an element is a common mistake. When creating elements, such as a list, figure, note, caution, or warning, be sure to include the end tag. Check your markup carefully especially if you have nested one element within another, such as a figure within a list,
Errors can also be introduced by using an incorrect entity name. In most instances, it is simply a misspelled word. In other cases, an entity name may have been changed, but cross-references to the original name were overlooked. When you change an entity name, remember to search your source file (or files) for all instances of the entity name.
Similarly, changing the ID assigned to an element affects any cross-reference or link to that topic.