Hello John,
Thank you for your question about the flashing screen. We made some very minor changes to the layout, but none I can think of that cause this.
1. When you say "flashing on and off," do you mean that sometime pages load, and sometimes not? Or do you mean that it flickers.
2. Could you try another browser?
3. What screen resolution are you using?
I use Firefox on MacOS also, so I can try to reproduce it.
bidslammer