Version 4.2 displays warning messages

Me too. I’ve reverted back to the old version.

rmh625:

If you have a backup of your site (before you updated the plugin). Just grab the “all-in-one-favicon” folder, and drag it into your plugins folder via FTP. This will override the new version you just updated to.

OR, sometimes the developer keeps old version on their site. You could look here:
http://www.techotronic.de/plugins/all-in-one-favicon/

I just update my all in one fav icon plugin too and had the same warnings, but its a simple fix and just a little mistake in the coding of that file.

Simply head to the file in the warning and change the following lines of code from:

'frontendICO' => _('ICO',AIOFAVICON_TEXTDOMAIN),
        'frontendGIF' => _('GIF',AIOFAVICON_TEXTDOMAIN),
        'frontendPNG' => _('PNG',AIOFAVICON_TEXTDOMAIN),
        'frontendApple' => _('Apple Touch Icon',AIOFAVICON_TEXTDOMAIN)
      );

      //mapping of favicon types to translatable Strings
      $this->aioFaviconBackendMap = array(
        'backendICO' => _('ICO',AIOFAVICON_TEXTDOMAIN),
        'backendGIF' => _('GIF',AIOFAVICON_TEXTDOMAIN),
        'backendPNG' => _('PNG',AIOFAVICON_TEXTDOMAIN),
        'backendApple' => _('Apple Touch Icon',AIOFAVICON_TEXTDOMAIN)

Change to:

'frontendICO' => __('ICO',AIOFAVICON_TEXTDOMAIN),
        'frontendGIF' => __('GIF',AIOFAVICON_TEXTDOMAIN),
        'frontendPNG' => __('PNG',AIOFAVICON_TEXTDOMAIN),
        'frontendApple' => __('Apple Touch Icon',AIOFAVICON_TEXTDOMAIN)
      );

      //mapping of favicon types to translatable Strings
      $this->aioFaviconBackendMap = array(
        'backendICO' => __('ICO',AIOFAVICON_TEXTDOMAIN),
        'backendGIF' => __('GIF',AIOFAVICON_TEXTDOMAIN),
        'backendPNG' => __('PNG',AIOFAVICON_TEXTDOMAIN),
        'backendApple' => __('Apple Touch Icon',AIOFAVICON_TEXTDOMAIN)

All that I have done is added an extra _ to each line (changing each _ to _e would also work, but I thought adding another _ looked easier to the eye when checking over the code in the future), which fixes the problem and will stop displaying the warnings 🙂