For the most part prefs,js is not considered a user editable file.

Specifically, which preferences do you want to change in the prefs.js file?

You normally make changes to prefs on the about:config page if you really need to do this and not by editing the prefs.js file. You shouldn't double-click the prefs.js file as that makes Windows see the file as a JScript file and not as the text file that it is.

Thanks. I need to allow cut and paste in Firefox.

That is no longer possible because support for this has been removed.

• https://developer.mozilla.org/en-US/Firefox/Releases/29/Site_Compatibility#Security

You can use keyboard shortcuts if the buttons on the web page or other methods aren't working.

• Copy: Ctrl+C or Ctrl+Insert (Mac: Command + C)
• Paste: Ctrl+V or Shift+Insert (Mac: Command + V)
• Cut: Ctrl+X or Shift+Delete (Mac: Command + X)

Hi gbolton, in most cases you will find that you don't need a website's copy/paste buttons, but instead you can use one of these methods:

• To copy, select text, then either:
  • right-click it > Copy
  • Ctrl+c keyboard shortcut

• To paste, click to position the cursor, then either:
  • right-click > Paste
  • Ctrl+v keyboard shortcut

These two methods work thoughout most of Windows, and if one doesn't work the other usually does.

Thanks for the info. Problem solved.