Final answer:
In Floodlight tag's iFrame code, the unique activity is identified by the "type" and "cat" elements, which signify the advertiser ID/group and the specific activity.
Step-by-step explanation:
The unique activity in a Floodlight tag's iFrame code is identified by the "type" and "cat" elements. The "type" element signifies the advertiser ID and the group of Floodlight activities, while the "cat" element is the activity tag string that stands for a specific activity within that group. These are the most important elements to differentiate one Floodlight activity from another when tracking conversions or other user actions.
The HTML elements of a Floodlight tag's iFrame code that identify the unique activity are -u1 and "fls". These elements are used to capture and transmit information about the specific action or event that the tag is tracking. For example, if the Floodlight tag is tracking a purchase, the -u1 element could contain the transaction ID, and the "fls" element could indicate that it is a purchase event.