The D.Skip tag

The anchor containing a null date "D.Skip":

    <A Name="D.Skip"></A>:

tells the indexing script not to bother to go any further in when looking at the file - there's nothing else of interest.

This can be used just to cut down the amount of work the Perl Script has to do but it is also used to avoid re-indexing any index files the script has already created: the script writes (will write) a

    <A Name="D.Skip Index"></A>:

at the start of any index files it creates.