Pages suddenly refreshing to top of screen

For the past month or so my screen keeps refereshing to the top of the screen. I will be reading a news site and after a few minutes or so, at some point it just suddenly goes back to the top of the screen and i hae to rescroll down again to where i was.

Or lets say I am in Facebook, I will be answering someone in a post and suddenly it does it again so i have lost my spot and have to go look for it again.

I seem to think from memory that problems such as this can be screen resolution problems but i havent changed mine.

Im on Snow Leopard 10.7.5 , Macbook Pro, 1280 x 800 ( my highest and one I have always been at ) and am on Color LCD Calibrated.

Beyond this I havent any idea what it can be...

Any ideas please?

I am not even sure of the right term in order to look it up on google, refreshing pages? LOL 😕

I use Safari but I see its happening in FireFox as well

I am not sure if it happens in emails or not though. Off hand I havent noticed but perhaps i am not in them long enough??!!