Something strange started happening to my PC after accidentally clicking on an advert which was on the side of the page. Browser started acting slow, thought nothing of it and carried on playing, then suddenly my PC logged me off the user. I log back in and my screen is taken up by a 404 internet explorer page and doesn't let me view anything else, couldn't even bring up task bar. Luckily I had a restore point and everything is back to normal. This happened only after clicking the advert.