Not sure if this is classified as a pop up, depending on the web site they look different than the capture below & some are to fast to take a capture.My question is if it's not a pop up how to prevent it.It always seems to appear from either the right or left side on a web site. Spoiler: CAPTURE
Download Ublock Origin from the developer Gorhill to install in your browser it is the best privacy extension + blocker their is along with HTTPS everywhere and Umatrix. Sorry I am mobile rn so I can not give you more instructions or links.
Thanks,so it is a pop up, even though the capture i posted doesn't pop up but seems like part of the web site. Also some that look the same kinda pop up, they periodically slide from either the right or left side.
Sorry for the late reply; yes it is something like a popup I have seen them on a view sites also but I just use Umatrix to block them and if it does not then Ublock does.