I have updated the pages which list the Hertfordshire Trade Directories. The most important change is to update the link to the directories digitized as part of the Historic Directories project (which covers the whole country and not just Hertfordshire). I have also listed the Hertfordshire directories which have been digitized as part of the Ancestry data base. The chief loss is of the 1811 Holden directory which was available through the Genhound web site which closed in 2015.
It is not possible for me to scan every genealogy and history web site for other online copies of Hertfordshire directories - or cases where indexed by name information is available a genealogy web site - so if you know of any that I have missed please add a comment below.