1. A content output device comprising: at least one memory operable to store program codes; at least one processor that executes the program codes and operates as instructed by the program codes, the program codes including: image acquiring code that causes the at least one processor to acquire an image captured by an imaging device through a communication network, wherein the image device periodically captures the image at a preset time interval set by a timer connected with the at least one processor; characteristic element specifying code that causes the at least one processor to specify a characteristic element from the image acquired by the image acquiring code based on a first comparison between the image and a plurality of preset characteristic elements stored in a content memory, wherein the content memory stores content associated with at least one preset characteristic element from among the plurality of preset characteristic elements; difference specifying code that causes the at least one processor to specify an element included in a characteristic element of a current image and not included in a characteristic element of a previous image, which is a target of second comparison, as a different characteristic element between the previous image and the current image, the previous image being acquired prior to the current image and stored in a characteristic element memory; output code that causes the at least one processor to output content stored in the content memory and associated with the characteristic element related to the specified different characteristic element on a display device through the communication network; and count code that causes the at least one processor to count a number of differences between the characteristic elements in the previous image and the current image, wherein the output content being displayed on the display device is not switched in response to the counted number of differences between the characteristic elements in the previous image and the current image being less than a predetermined number, wherein the output content excludes a content related to a characteristic element that is common between the current image and the previous image.