11. A computer program product for identifying content in a document, the computer program product comprising: a computer readable storage medium, wherein the computer readable storage medium is not a signal, wherein the computer readable storage medium includes program instructions that when executed by a computer cause the computer to carry out the steps of: identifying within each document of a plurality of open documents, by a computing device, content corresponding to a particular subject matter category; in response to the computing device opening an additional document, identifying within the additional document, by the computer device, additional content corresponding to the particular subject matter category; providing, within the additional document, an indicator that visually distinguishes the identified additional content from the other content within the additional document; in response to the computing device opening a second additional document and content of the second additional document not corresponding to the particular subject matter category, determining a new subject matter category corresponding to the content of the second additional document; determining a majority of the plurality of open documents of the computing device relate to similar subject matter, wherein the particular subject matter category relates to the similar subject matter; in response to determining that the majority of the plurality of open documents of the computing device relate to the similar subject matter, assigning a weight to the similar subject matter and the new subject matter category, wherein the similar subject matter is more heavily weighted than the new subject matter category; and providing indicators that visually distinguish documents relating to the similar subject matter category from documents relating to the new subject matter category.
11. A computer program product for identifying content in a document, the computer program product comprising: a computer readable storage medium, wherein the computer readable storage medium is not a signal, wherein the computer readable storage medium includes program instructions that when executed by a computer cause the computer to carry out the steps of: identifying within each document of a plurality of open documents, by a computing device, content corresponding to a particular subject matter category; in response to the computing device opening an additional document, identifying within the additional document, by the computer device, additional content corresponding to the particular subject matter category; providing, within the additional document, an indicator that visually distinguishes the identified additional content from the other content within the additional document; in response to the computing device opening a second additional document and content of the second additional document not corresponding to the particular subject matter category, determining a new subject matter category corresponding to the content of the second additional document; determining a majority of the plurality of open documents of the computing device relate to similar subject matter, wherein the particular subject matter category relates to the similar subject matter; in response to determining that the majority of the plurality of open documents of the computing device relate to the similar subject matter, assigning a weight to the similar subject matter and the new subject matter category, wherein the similar subject matter is more heavily weighted than the new subject matter category; and providing indicators that visually distinguish documents relating to the similar subject matter category from documents relating to the new subject matter category. 15. The computer program product of claim 11 , wherein identifying within each document of a plurality of open documents, by a computing device, content corresponding to a particular subject matter category includes searching one or both of text and graphical elements of the additional document for the additional content.