Squarespace Site Tweaks & Integrations

I need a quick but polished tune-up on my Squarespace site. First, the header and footer look fine on desktop, yet they slide out of alignment on certain screen sizes. I want them snapping neatly into place whether the visitor is on a big monitor or a small phone... (Budget: $10 - $30 USD, Jobs: CSS, Google Analytics, HTML, Squarespace, Web Design, Web Development)