Account for header height

netbox/project-static/css/base.css

@@ -65,7 +65,7 @@ footer p {
 /* Scroll the drop-down menus at or above 768px wide to match bootstrap's behavior for hiding dropdown menus */
 @media (min-width: 768px) {
     .navbar-nav>li>ul {
-        max-height: 80vh;
+        max-height: calc(80vh - 50px);
         overflow-y: auto;
     }
 }
@@ -73,7 +73,7 @@ footer p {
 /* Collapse the nav menu on displays less than 980px wide */
 @media (max-width: 979px) {
     #navbar {
-        max-height: 80vh;
+        max-height: calc(80vh - 50px);
         overflow-y: auto;
     }
     .navbar-header {