There're also things like the Ghostery add-on, which detects and blocks web bugs, ad beacons and tracking pixels. Although I have found that it doesn't automatically block every one, it just tells you they're there. And if course it wouldn't work if the bug was set up by someone on their own server, or was a small provider like LjToys that ghostery is not aware of. I was quite surprised by how many there were- some web pages have them in double digits- that's over 10 different ad companies following you about at any 1 time.