MichaelCrawford parent
Strictly speaking a one-pixel gif could be legitimate. What I find especially sketchy is that the URLs that my browser actually fetches are huge, long and full of query parameters.
I do not want one-pixel gifs, because the only use of such techniques is exploiting the HTTP "referer" field.
They used to be somewhat legitimately used for spacing and sizing table-based HTML layouts (through the mid-2000s or so). That's rarely done today -- layout is in CSS and gifs are generally used for tracking.