...you might consider the standalone version of Tidy for html...
I agree. It's very nifty indeed, easy to use and highly configurable.
Something as simple as:
my $in = 'bad.html';
my $out = 'tidied.html';
my $err = 'tidy.err';
my $cnf = 'tidy.cnf';
-config => $cnf,
-file => $err,
-output => $out,
can be easily adapted to process a list or even a local copy of a web site. The config file can be tweaked to be severe or lenient to taste.
You can easily interrogate all the error files to get a good picture of how bad the html is (and there is a lot of it about!).
Again, I agree. Why bother to go to a lot of trouble when there is a very clever bit of kit available.