This used to happen to me quite a bit but the problem has now disappeared. I think, for me, it was because I had limited memory on my old Mac, my browser was memory-heavy - I was using Firefox then - and there are peak times when our ISP provider loses it a bit. Since purchasing a Mac with a lot of memory and changing from Firefox to SRWare Iron, which is a memory-light browser, I've had no more trouble. I know a lot of you like Firefox but Mrs SJ uses it and I am forever sorting out some glitch or other, usually because it has too many bells and whistles, all of which want to run at the same time.