|It has appeared on the read message page while reading an individual message such as:|
And it has appeared on the subjectmark page:
It appears on the left side of the page each time and it blocks the text so it cannot be read, here's a sample pic which I copied for you:
Most of the time it goes away when I reload the page... there is no X to X out of that pop up, but there is a small question mark at the top right corner which curiously did not show up on this copy, but the one time I did click on that question mark, this page came up which I then clicked out of:
I will let you know if/when it appears again and on which page...