Since last few updates of Firefox our beloved Firebug is integrated into the Firefox Developer Tools and a lot of people including me don't like what happened to Firebug.
The built-in developer tools have a very ugly menu system and messed up usability.
So, what are the alternatives to the Firefox Developer Tools? Is there a tool with the same usability as Firebug?
Following Sebastian's advice I've downloaded old Firefox portable v47 from here:
https://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox%2C%20Portable%20Ed./Mozilla%20Firefox%2C%20Portable%20Edition%2047.0.1/
and I'm using it with Firebug only for development. According to Firebug's website 47 is the last compatible version of Firefox:
https://getfirebug.com/downloads
To avoid compromising on security, for normal browsing I use updated version of Chrome.
Alternatives are:
Downgrading the version is not advisable, So instead of that go to the browser console and type your respective xpath in the mentioned syntax $x('path') to validate your XPath.
Or can find other similar plugin. So far I find the Plugin 'Xpather' in http://xpath.alephzarro.com/ link. But I still would like to reactivate Firebug to rework by setting the preferences browser.tabs.remote.autostart, browser.tabs.remote.autostart.1 and browser.tabs.remote.autostart.2 to false via about:config.