An unrelated internet search brought me to an article describing the lack of universal support for fixed-position elements on mobile browsers. So I've made the header static again, and will 'upgrade' the non-mobile design to a fixed-position header. I haven't decided yet whether I will put the sitemap back into the mobile design's footer.
Changed footer background and tried to add a textured background image to the social media section of the footer. For some reason, the image doesn't show up, and I can't figure out why.