HTML CSS
(real quick examples)
<header id="page-head"> HEADER </header>
<main id="page-main"> CONTENTS </main>
#page-head { FIX HEADER TO TOP position: fixed; top: 0; z-index: 9; DIMENSIONS width: 100%; height: 30px; }
MAKE SURE CONTENTS NOT COVERED UNDER HEADER #page-main { margin-top: 30px; }
<header id="page-head"> HEADER </header>
<nav id="page-nav"> <a href="#">NAV</a> <a href="#">NAV</a> <a href="#">NAV</a> </nav>
<main id="page-main"> CONTENTS </main>
STICKY HEADER ON TOP #page-nav { position: sticky; top: 0; z-index: 9; }