The Webtatic EL5 repository was set to use https protocol in July last year, however since RHEL and CentOS 5 are unable to verify the certificate, there wasn't much security gain from this.
Because of this, the repository is switching back to http protocol. The https protocol will be supported still for the previous webtatic5-release version till 18th August 2016. After then, the repository will only be available on http, but still accessible to SSL clients that support Server Name Indication (SNI). RHEL/CentOS 5 don't support SNI, however.
Additionally, RHEL 5 is going to be at it's End of Production Phase on 31st March 2017, CentOS 5 will become end of life around this point.
Because of this, the Webtatic EL5 repository will become end of life (EOL) at that point, and it's packages will be archived.
* As of now, new installs and upgrades of the webtatic5-release for EL5 will use http protocol for package installs (as it did July last year)
* On 18th August 2016, https protocol for EL5 will no longer be supported by RHEL/CentOS 5 yum package manager
* On 31st March 2017, the EL5 repository will become end of life (EOL), and be archived.