The mp4s on your site are killing your load time. Start by making them smaller in display size and compressing them more. If that doesn't work out place them on Youtube, Vimeo or Amazon S3 and embed them. I think you have some other issues but you need to take care of this first to see how it works once this is corrected.

Your worst problem is this is happening on the front page of your site too. If you are not seeing it it is because you have that page cached locally in your browser.