On a client computer a request is sent to a server computer to open a first portion of a document. The document is stored at the server computer. The first portion of the document is smaller than the entire document. The request includes information used by the server computer to determine a size of the first portion of the document. The first portion of the document is received from the server computer. A second portion of the document is rendered on a display screen on the client computer. The second portion of the document is a subset of the first portion of the document. When the client computer determines that the user has scrolled a third portion of the document and that more of the document is available at the server computer, a second request is sent to the server computer to open an additional portion of the document.