15. A system comprising: a processor configured to execute instructions stored in a non-transitory computer-readable medium; wherein the instructions comprise an editor application configured to perform operations comprising: identifying a pattern in a visual presentation of a plurality of output elements as displayed in the received output presentation, wherein the pattern corresponds to the source element; receiving a modification to an output element from the plurality of output elements in the received output presentation; determining, based on identifying the pattern, a corresponding modification to the source element that corresponds to the modification to the output element; and based on identifying the pattern, applying the corresponding modification to the source element in response to receiving the modification to the of the plurality of output elements.
15. A system comprising: a processor configured to execute instructions stored in a non-transitory computer-readable medium; wherein the instructions comprise an editor application configured to perform operations comprising: identifying a pattern in a visual presentation of a plurality of output elements as displayed in the received output presentation, wherein the pattern corresponds to the source element; receiving a modification to an output element from the plurality of output elements in the received output presentation; determining, based on identifying the pattern, a corresponding modification to the source element that corresponds to the modification to the output element; and based on identifying the pattern, applying the corresponding modification to the source element in response to receiving the modification to the of the plurality of output elements. 16. The system of claim 15 , wherein the output presentation comprises a web page; wherein identifying the pattern comprises identifying a layout of the plurality of output elements; wherein determining the modification to the source element corresponding to the modification to the of the plurality of output elements comprises determining a modification to one or more elements of a template file specifying the layout.