15. The computer device according to claim 12 , wherein said identification information includes information representing a URI for said first document.
12. A computer device with a display configured to load and display documents, and comprising one or more computer processors which execute computer program code to perform: transmitting first and second download requests for first and second documents respectively, the first and second download requests identifying different domains as respective origins from which the first and second documents are to be loaded; executing a script in said first document which has been loaded by a user agent implemented on the computer device in response to the first download request, said script providing data to be sent to said second document; retrieving, from information collected by the user agent when the first document was loaded in response to the first download request, identification information uniquely identifying said first document and an-said origin of said first document; and sending a message including said data and said identification information to said second document which has been loaded by the user agent in response to the second download request, wherein said script in said first document invokes a method implemented in said user agent, said method being defined to receive the data to be exchanged, receive information identifying said second document, extract said information identifying said origin of said first document, and pass said information to be exchanged and said information identifying said origin of said first document to said second document, and wherein said first and second documents and the structure of said first and second documents are addressed according to application programming interfaces (APIs), defined in a Document Object Model (DOM) module that is part of said user agent, and the computer device is further configured to perform: instantiating, upon loading said first and said second document, two objects representing said first and second documents.