function make_nav_box(a){nav_box_start();make_opt("Introduction",".",a);make_opt("Background","day0.html",a);make_opt("Day 1","day1.html",a);make_opt("Day 2","day2.html",a);make_opt("Day 3","day3.html",a);make_opt("Day 4","day4.html",a);make_opt("Day 5","day5.html",a);make_opt("GPS Tracks","tracks.html",a);nav_box_end()};