This means that at those locations you have something that looks like this:
<a><a>link title</a></a>
It is invalid to put a link inside of another link. That's what it is complaining about. Fix the html, and you'll be good.
The error is telling you what files and where to fix them.
So the file e_7_ch1-1.xhtml has the mistake I showed above. I think it is of the format (column number, line number). So the first error is 846 lines into that file, and 16 characters into that line.
Hope that helps.
|