If you start from file:///C:/ and click your way to that folder, then right-click the address bar > Copy can you see any difference from the URL that doesn't work?

By the way, version 27 is not secure; Mozilla discloses security flaws after each new release. Is something holding you back from upgrading to Firefox 29? Please let us know so we can suggest solutions or workarounds.

P.S. Firefox 30 will be released later this week.

jscher2000, thank you for the care! If I copy the link from the page body and put it in address bar, it works, and is coded with %xx. But it doesn't work from page inline - when a call to Windows File Explorer is made. The link works when network.protocol-handler.expose.file = true but not when false.

Can I use in Firefox 30 the old interface (not Australis)? Thank you!

May be the problem is that Firefox calls explorer.exe (or other Windows programs to handle a file) encoding the filename with %-encoding, which is not recognized by the application. Or FF uses encodeing not compatible with program called.

Hmm, does Firefox use a different URL than IE does? Or does IE convert it to a more file-system friendly syntax when passing it to the file system?

Regarding the interface of Firefox 30, you will need an extension to make any heavy modifications to the UI. This one is popular: https://addons.mozilla.org/firefox/addon/classicthemerestorer/

I think the problem can be that:

Calling Windows application from the link on UTF-8 page, Firefox sends a parameter (filename) encoded in UTF-8, which is not accepted by Windows application in case of non-latin characters. Workaround needed.

You can use extensions like Classic Theme Restorer and code in userChrome.css to restore a lot of the changes that were made to Firefox when the Australis appearance landed.

See also:

• https://support.mozilla.org/kb/how-to-make-new-firefox-look-like-old-firefox

• https://support.mozilla.org/kb/common-questions-after-updating-to-new-firefox
• https://support.mozilla.org/kb/learn-more-about-the-design-of-new-firefox

I spent many days customizing Firefox and am not going to start over, again. I'm not a specialist in coding userChrome.css, am very busy with other stuff. It's better if developers restore ALL of the changes once, than thousands of users will spend many days each. Dixi.

Anyway, my main question is:

How to make Firefox send a parameter (filename) to a Windows application, encoded in Windows-1251 instead of UTF-8?

Would be very grateful.