Screen flashes black when loading or leaving a campaign page with a moving background.

When entering (opening) or closing a page with a moving background (example: <a href="https://app.roll20.net/campaigns/details/445207/ma" rel="nofollow">https://app.roll20.net/campaigns/details/445207/ma</a>... ) the whole screen (not just the webpage) flashes black for a half second before returning to nformal. This occurs reliably in both Firefox and Chrome. OS: Windows 8.1 Update 1 Browser: Firefox 30.0 and Chrome 35.0 (with extensions disabled) Graphics Driver: NVIDIA GeForce 337.88 and 340.43