1. A computing device configured to execute a hosted application, comprising: a processor and storage, where an operating system is installed on the computing device that configures the processor to create a computing environment; an application platform application stored in the storage of the computing device, where the application platform application comprises: a rendering engine process configured to: render pages within the computing environment created by the operating system by interpreting instructions written in a rendering language; and implement a virtual machine configured to execute instructions written in a scripting language; and an integration process that enables instructions executing within the virtual machine to modify the computing environment; at least one hosted application comprising: a background page file including instructions in the scripting language: wherein the virtual machine is configured to parse the instructions in the scripting language contained within the background page file to configure the processor to: download at least one remotely hosted file containing instructions in the rendering language for rendering a web page; modify the instructions written in the scripting language within the at least one downloaded file in accordance with a predetermined page modification rule to create at least one modified file; build a document object model (DOM) based upon at least the instructions in the at least one modified file; and modify the DOM in accordance with a predetermined DOM modification rule to create a modified DOM; and wherein the rendering engine process is configured to render a user interface page based upon the modified DOM generated by the execution of the background page.