1. A system comprising: one or more hardware processors configured to: receive, from a client device over a computer network, a request that references a first uniform resource locator (URL) by which a single document is locatable for display in a browser running on the client device, the first URL corresponding to a first state in which the single document has a first appearance, the first appearance defined by presence of first content without second content within a portion of the single document; and provide, via the computer network, the single document in its first state with its first appearance to the browser in response to the request and based on the first URL corresponding to the first state, the single document in its first state including a control usable to invoke a second state in which the single document has a second appearance, the second appearance defined by presence of the second content without the first content within the portion of the single document; and detect, via the computer network, by the one or more hardware processors, use of the control at the client device to invoke the second state of the single document, the control referencing a second URL by which the single document is locatable for display in the browser; the browser displaying the single document in its second state with its second appearance and the second URL without requesting from a server content associated with the single document and in response to the use of the control; and map, by the one or more hardware processors, the second state of the single document to the second URL by storing a correspondence relationship between the second URL and data that defines the second appearance of the single document.