After having discovered numerous HTMLDiff Projects out there, I found myself trying 3 or 4 of them out.
They all had particular traits that both fit and didn't fit what I wanted, so I thought I should write about them for others who are looking for good HTMLDiff software.
This posts will be on the the C HTMLDiff code I stumbled on.
shell_exec) is unbelievably fast. Compared with my usage of the the PHP library Visual Diff (moved over to http://gitorious.org/htmldiff), it's not even comparable
It's a solid library, but unfortuantely, not of use to me right now.