Now working again. (A great tool I have used for many years.) But
first I had to do a clean install of Firefox 57 (new profile) and then
install HTML Validator. Apparently there was some junk in my VERY old
profile that caused a problem with the new Firefox and new HTML
Validator. The source displayed by the Inspector showed a wtx-context
added to the HTML tag and to several others. That was not in my actual
source code. The Validator did not like that attribute and put up a
warning. Even worse, the Validator would not detect any errors in an
intentionally buggy test file I created. Doing the clean install fixed
all that.

I wish there were a keyboard shortcut to invoke the HTML Validator in
this new environment, e.g., as Ctrl-Shift-C, Ctrl-Shift-S, etc. do for
other tools. I have programmed my mouse to do a Ctrl-Shift-I, but then
have to click on the HTML Validator tab.

When I try to go to http://users.skynet.be/mgueury/mozilla, I get a
timeout. Is that site no longer available? If I do a tracert for
users.skynet.be, it steps thru almost 20 nodes, but finally times out in
Belgium. Jeff

very good

Ok