If you use Arch Linux and just ran a system update, you will probably have a problem that make you unable to run firefox, chromium and many other applications. If you run the command to open firefox or chromium in the terminal, you will have the error saying:
libpng14.so.14: cannot open shared object file: No such file or directory
The reason of this problem, according to the Arch Linux main page, is because "recent releases of libpng and libtiff have required a rebuild of all packages that depend on them; these have just been moved from [testing] to the main repos."
To fix that problem, you need to check and rebuild the unofficial packages (mostly those that came from the AUR) that depend on libpng, especially those with a cairo prefix. To know which package that need to be rebuilt, you can run this command: