1. A method comprising: rendering a web page for display on a client device, wherein the rendered web page includes a first document and a first advertisement that is based on the first document; determining that a first scroll position of the rendered web page has a first characteristic; responsive to determining that the first scroll position of the rendered web page has the first characteristic, (i) requesting and receiving a second document from a content server device, and (ii) based on the second document, requesting and receiving a second advertisement from an advertisement server device; and re-rendering the web page for display on the client device, wherein the re-rendered web page includes content from the first document, content from the second document, the first advertisement, and the second advertisement, wherein not all content from the first document and second document is displayed on the re-rendered web page, wherein the first advertisement is based on non-displayed parts of the first document, and wherein the second advertisement is based on non-displayed parts of the second document.
1. A method comprising: rendering a web page for display on a client device, wherein the rendered web page includes a first document and a first advertisement that is based on the first document; determining that a first scroll position of the rendered web page has a first characteristic; responsive to determining that the first scroll position of the rendered web page has the first characteristic, (i) requesting and receiving a second document from a content server device, and (ii) based on the second document, requesting and receiving a second advertisement from an advertisement server device; and re-rendering the web page for display on the client device, wherein the re-rendered web page includes content from the first document, content from the second document, the first advertisement, and the second advertisement, wherein not all content from the first document and second document is displayed on the re-rendered web page, wherein the first advertisement is based on non-displayed parts of the first document, and wherein the second advertisement is based on non-displayed parts of the second document. 7. The method of claim 1 , wherein determining that the first scroll position of the rendered web page has the first characteristic comprises determining that the first scroll position of the rendered web page is above a first threshold scroll position, and wherein re-rendering the web page for display on the client device comprises re-rendering the web page to represent the second document followed by the first document.