Body and header padding error (possibly jquery)

Hi there, I’m having an issue with the body of my pages jumping into the header when a page is refreshed. It happens chronically on every page in Safari and Chrome. It has happened in Firefox, but doesn’t seem to occur when I’m logged into the back end.
Check out animateaway.org and go to any page, hit refresh and see the padding or margin between the body and header disappear. One time it did the opposite and provided too much space.
My buddy who knows much about code said the problem is thus:

“You’re not importing jquery properly. There’s a js file ‘superhero.js’ that changes the padding based on the ‘masthead-wrap’ height…the issue is that the script that resizes the header isn’t working right because there’s an issue loading a script that doesn’t exist.”

We’ve hit a brick wall. I hope one of you fine upstanding supporters will be able to figure this one out for us. Thanks in advance!