Background does not display

A user recently informed me that when he logged onto my site, the content fields displayed but not any of the template elements (header, background, footer). This is not a global issue, nor is it a ongoing one with this user (who views the site on a Mac on Safari). I suspect that his computer resources were low and that the site was not displaying properly because a temporary memory issue prevented him from loading the site to completion. Can you think of any other reason why this issue may have taken place?

The site is https://thewire.jewishla.org