I am taking over this project. The previous developer left absolutely no documentation as to what was done.
I normally log onto 'built with' to find out what technologies were used, but that is not giving me much info.
At this point I am thinking it is on Magento or something, but I can not be 100% sure.
Try one of these online detection sites:
http://w3techs.com/sites/
http://builtwith.com/