11. A method comprising: receiving, by a page-assembling process executing in conjunction with a client rendering application executing in a client computing device, a call from a function call in a response portion received by the client computing device for generating a corresponding portion of a requested web page, the response portion further comprising markup-language code and one or more of one or more portions of content to be rendered by the client computing device, one or more resources, or one or more references to resources; and after receiving the call from the function call: identifying, by the page-assembling process, a place-holder identification (ID) parameter in the function call; accessing, by the page-assembling process, a model representation, generated by the client rendering application, of a structured document that comprises one or more place-holder code segments, each place-holder code segment being represented as a place-holder node in the model representation, each place-holder code segment and respective place-holder node having a corresponding place-holder ID parameter; identifying, by the page-assembling process, a place-holder node in the model representation by matching the place-holder ID parameter in the call to the corresponding place-holder node having a matching place-holder ID parameter; and inserting, or causing to be inserted, by the page-assembling process, the portions of content, resources, or calls to resources in the response portion into the model representation at a location in the model representation determined based on the corresponding matching place-holder node; wherein the response portion is one of a plurality of second response portions received by the client computing device subsequent to a first response portion received by the client computing device, each second response portion comprising a function call to the page-assembling process, markup-language code, and one or more of one or more portions of content to be rendered by the client computing device, one or more resources, or one or more references to resources; and wherein the first response portion comprises: the structured document for use by the client computing device to render a requested web page, the structured document comprising: markup-language code that comprises one or more place-holder code segments; a code segment for implementing the page-assembling process and comprising a function library; and one or more first resources or one or more first references to first resources.
11. A method comprising: receiving, by a page-assembling process executing in conjunction with a client rendering application executing in a client computing device, a call from a function call in a response portion received by the client computing device for generating a corresponding portion of a requested web page, the response portion further comprising markup-language code and one or more of one or more portions of content to be rendered by the client computing device, one or more resources, or one or more references to resources; and after receiving the call from the function call: identifying, by the page-assembling process, a place-holder identification (ID) parameter in the function call; accessing, by the page-assembling process, a model representation, generated by the client rendering application, of a structured document that comprises one or more place-holder code segments, each place-holder code segment being represented as a place-holder node in the model representation, each place-holder code segment and respective place-holder node having a corresponding place-holder ID parameter; identifying, by the page-assembling process, a place-holder node in the model representation by matching the place-holder ID parameter in the call to the corresponding place-holder node having a matching place-holder ID parameter; and inserting, or causing to be inserted, by the page-assembling process, the portions of content, resources, or calls to resources in the response portion into the model representation at a location in the model representation determined based on the corresponding matching place-holder node; wherein the response portion is one of a plurality of second response portions received by the client computing device subsequent to a first response portion received by the client computing device, each second response portion comprising a function call to the page-assembling process, markup-language code, and one or more of one or more portions of content to be rendered by the client computing device, one or more resources, or one or more references to resources; and wherein the first response portion comprises: the structured document for use by the client computing device to render a requested web page, the structured document comprising: markup-language code that comprises one or more place-holder code segments; a code segment for implementing the page-assembling process and comprising a function library; and one or more first resources or one or more first references to first resources. 17. The method of claim 11 , wherein each second response portion comprises a callback function that comprises the markup language code, one or more portions of content, one or more resources, or one or more references to resources in the second response portion.