lucy24 - 8:26 pm on Apr 7, 2013 (gmt 0)
The bandaid fix goes something like this
RewriteRule ^([^.]+\.html)/ http://www.example.com/$1 [R=301,L]
meaning "If there is a slash after the .html, redirect to form of URL that stops at .html". No closing anchor in the pattern, so there might be more stuff after the directory slash.
This is one of the many rules that you don't need to add unless you're actually getting requests for bogus URLs. Others include rules for intercepting multiple directory slashes, and rules for html files with attached query string (assuming you're not secretly parsing .html as .php).
Does the link actually lead to a real resource?
By default you can add any kind of garbage after html-- or any other extension used with static files-- and it will have no effect on the page.