Pages glitching in preview

Files will often show up with random colors, half pages missing, or just just show a blank page if you are not logged into the website while previewing the downloaded files. There is no consistency with the files, sometimes they work while other times, they just wont show up; however, once downloaded to your computer, everything shows up fine. I have tried clearing the cache and updating all of the plugins but the problem persists.Linked is just one of the pages we are having problems with.

The page I need help with: [log in to see the link]