eye symbol on computer screen ????

[gtfpv]

everynow and then an eye symbol with a red circle with a line through it appears on my screen . at the bottom of the screen slightly to the right of centre .
if i put my curser on it it says privacy report . if i click on it it does nothing .
i dont know why it appears or why it dissapears ? it appears on this site and many others at random .
what is it ?? anyone know .