13. The system of claim 11 , wherein identifying one or more characteristics associated with the content includes identifying font characteristics associated with the content, and wherein modifying one or more characteristics of the advertisement includes modifying a font of the advertisement based on the font characteristics associated with the content.
11. A system comprising: a processor; and a computer-readable medium operatively coupled to the processor and including instructions, which, when executed by the processor, causes the processor to perform operations comprising: identifying content of a document; identifying an advertisement to be displayed in the document; identifying one or more characteristics associated with the content; and modifying one or more characteristics of the advertisement based on the characteristics associated with the content of the document.