> Why Webhtttrack opens in Opera browser, and not in
> Firefox?> How can I configure which browser has webhttrack to
> use by default?
webhttrack attempt to find the first matching program within:

x-www-browser www-browser iceape mozilla firefox icecat iceweasel abrowser
firebird galeon konqueror opera chrome chromium chromium-browser netscape

You may want to alias www-browser to firefox (/etc/alternatives), for
example.