[stavros]

The fact that you don't see it doesn't mean it doesn't exist. I make up a unique file, put it on site X and ask your browser to cache it. I try to load the same file on site Y and time how long it takes. If it's instant, site Y knows you visited site X.

Tadaaa! Tracking.

[cjbgkagh]

I said I ‘can see’ I already understand that. Hence the whitelisting on files that are not unique / created for this purpose.

[stavros]

Ah, my bad, sorry.