Problems with OpenNav/CloseNav

[gbowne1]

In the Firefox v105 (x64) console in Debian Linux

This script:

<script>
      function openNav() {
        document.getElementById("TAOTSideNav").style.width = "250px";
        document.getElementById("main").style.left = "250px";
        document.getElementById("main").style.opacity = "0.8";
      }

      function closeNav() {
        document.getElementById("TAOTSideNav").style.width = "0";
        document.getElementById("main").style.left = "0";
        document.getElementById("main").style.opacity = "0.8";
      }
      var max_width = window.matchMedia("(max-width: 768)");
</script>

says:

Uncaught TypeError: document.getElementById(...) is null for both openNav() and closeNav()