What Site Builder Build Facebook?

[Fasr]

Is Facebook Build By Joomla?

[Jawad]

PHP.

HTML isn't a programming language (it's a markup language), nor is CSS, however, they're naturally both used in the creation of almost all websites.

I don't think you have a concrete understanding of how sites work: PHP is a PreHypertext Processor.

Facebook's server environment is unknown and not released to the public. It is believed to be custom developed.

Facebook uses Thrift for management of scripts, which allows for the use of python, perl, ruby, c++ and java: this is what gives the FBML and the Facebook API its' versitility.

The database software is based on the ubiquitous MySQL, but with a twist: Cassandra allows for faster data manipulation on a cloud network.