AOL Instant Messenger's installation process automatically installed an extra URI scheme ("protocol") handler into some Web browsers, so URIs beginning "codice_1" could open a new AIM window with specified parameters. This was similar in function to the codice_2 URI scheme, which created a new e-mail message using the system's default mail program. For instance, a webpage might have included a link like the following in its HTML source to open a window for sending a message to the AIM user "notarealuser":