This has been happening to me for several days now. When it pops up - I go back one page then go forward one page and it's gone. Wondered if I should worry about this - happens about 2-3 times each morning, as I'm looking at all the posts. Wish I was more computer literate and hope there is nothing wrong. It's a black line at the top of the page that says "Warning....." and it's from MacAfee.