Firefox css issue

I was wondering how to get the header image to show only on the home page of my free Radiate theme and I found the following CSS edit:

#parallax-bg {
display: none;
}

.home #parallax-bg {
display: block;
}

.page:not(.home) #masthead {
margin-bottom: 50px;
}

At first, it worked – header image only on home page. Then the image disappeared and only a blank appeared on the homepage BUT only in Firefox.

I returned the CSS to the original code:

#parallax-bg {
position: fixed;
top: 0;
left: 0;
right: 0;
bottom: 0;
z-index: 1;
}
#page {
position: relative;
z-index: 888;
}
#masthead {
}

but the behaviour remained in Firefox, ie no header image.

This doesn’t only occur on my local machine, either, it’s in any Firefox browser.

I’ve hidden the header image now as the site is live and I don’t want the problem to be viewable, so I don’t know if you need the URL, but here it is: verandaphangan.com.

Thoughts appreciated,

wpchad