This directory (and version of CentOS) is deprecated. For normal users,
you should use /5/ and not /5.7/ in your path. Please see this FAQ
concerning the CentOS release scheme:

https://wiki.centos.org/FAQ/General

If you know what you are doing, and absolutely want to remain at the 5.7
level, go to http://vault.centos.org/ for packages. Please keep in mind that 5.7 no longer gets any updates