19. A system comprising: a first computer; a content viewer operably installed on the first computer; a content object accessible to the first computer via the content viewer; a second computer different from the first computer; a content viewer readable code component accessible to the second computer, the content viewer readable code component including dynamically selectable characteristics, the content viewer readable code component being useable with a plurality of different content viewers; combining the content viewer readable code component into the content object; serving the combined content object to a user system; and changing a portion of the content object upon execution of the content viewer readable code component at the user system without altering the remainder of the content object.
19. A system comprising: a first computer; a content viewer operably installed on the first computer; a content object accessible to the first computer via the content viewer; a second computer different from the first computer; a content viewer readable code component accessible to the second computer, the content viewer readable code component including dynamically selectable characteristics, the content viewer readable code component being useable with a plurality of different content viewers; combining the content viewer readable code component into the content object; serving the combined content object to a user system; and changing a portion of the content object upon execution of the content viewer readable code component at the user system without altering the remainder of the content object. 24. The system as claimed in claim 19 wherein the dynamically selectable characteristics of the content viewer readable code component include at least one characteristic from the group: shape, color, text, and category.