This happened recently, few days ago - I logged off the computer, then turned it off but Answerbank's page was still visible even thought the screen was black (really dark). Why did this happened? I am 100% sure Answerbank was visible, and it was not an image in my photographic memory, or that my vision was playing tricks and fooling me.
Thanks for reading my question and your explanations.
Had you been staring at the screen for a long time? Stare at the screen for about 30 seconds then close your eyes tightly, you can still sometimes see an image of what you were looking at.
Is it possible that the image didn't move for some time, and became somehow burned on the screen? I am not remotely technical but this happened to me one time, I'd left the eBay screen up with no screensavers and I could see a sort of shadow of it on the screen after I'd closed down. The techies will know what it is, I am sure, but I as told that it was a bad thing, and that we should make sure that there are some moving items on the screen all the time if you leave it for a while.
I thought of that, but, that was impossible because I'm always busy doing other things while on here. Hardly ever focus at the computer screen for a 20 minutes period at one time.
LCD screens don't suffer from screen burn but they can suffer from temporary image retention if the same picture has been displayed for a long time. (apparently it can become permanent if the same picture is displayed for a silly length of time, I've never seen it though)
Plasma and CRT screens also suffer from image retention but the retention can turn into permanent screen burn fairly quickly if they are left for too long.
What is is baffling me - I logged off. I don't have a fancy background, my screen is blue. The machine was then turned off and the screen changed to black.