Disclosed are various embodiments relating to generating portions of network pages associated with a network site, where the portions of the network pages are generated by page generation code that uses a subset of aggregated data provided to it. A request for a network page is received from a first party. Data is aggregated from one or more data sources in response to the request. Each data source provides multiple data items using a multipart encoding. Page generation code supplied by the first party is executed to generate at least a portion of the network page in response to receiving a subset of the data which is used by the page generation code. The page generation code is able to access the subset of the data as predefined variables.