1. A non-transitory computer-readable medium embodying at least one program executable in at least one computing device, the at least one program comprising: code that, in response to receiving a request for a network page from a client, aggregates data from a plurality of data sources for use by page generation code supplied by a customer, the network page being associated with a network site hosted by a hosting provider on behalf of the customer; code that executes the page generation code in response to the request, the page generation code being configured to generate at least a portion of the network page, the code that executes being configured to provide the data that has been aggregated to the page generation code as a plurality of predefined variables, the code that executes the page generation code being under control of the hosting provider; code that executes error page generation code supplied by the customer to generate an error network page in response to determining that an internal server error has occurred, the error network page being customized for the network site by the customer; code that sends the error network page to the client; and wherein execution of the page generation code is terminated in response to the error.