Given that tracking occurs on the so-called Invisible Web, it initially appears odd that so many mechanisms are images. However, when investigating the images themselves, it is clear they provide little indication as to whom they belong to, and thus users are kept in the dark as to their purpose or presence. An examination of the top 100 requested images determined that only 24% contained information that would alert the user they had initiated contact with a third party. Many images were only a single pixel in size, and are often referred to as tracking pixels as their only purpose is to initiate HTTP requests. The most popular image, found on 45% of pages, was a single tracking pixel with the name utm.gif, which is part of the Google Analytics service. The second most popular image is the clearly identifiable Facebook “Like” button that was found on 16% of pages. It is unclear how many users elect to “Like” an illness, but Facebook is able to record page visits regardless if a user clicks the “Like” button, or if they