diff --git a/src/components/ScrollToTop.jsx b/src/components/ScrollToTop.jsx
index 0f8ce0a..2947388 100644
--- a/src/components/ScrollToTop.jsx
+++ b/src/components/ScrollToTop.jsx
@@ -4,10 +4,23 @@ import { useLocation } from 'react-router-dom'
 export default function ScrollToTop() {
   const { pathname, hash } = useLocation()
 
-  // Cross-page navigation: scroll to hash or top on route change
+  // Cross-page navigation: scroll to hash or top on route change.
+  //
+  // getElementById, not querySelector. querySelector THROWS on a fragment that
+  // is not a valid CSS selector, and an id starting with a digit is not one:
+  // `#8x8-implementation` and even `/#1` would throw here, in an effect inside
+  // the root route, and the error boundary would replace the header, the page
+  // and the footer with the error screen. The long-form service pages exist to
+  // be deep-linked from search results and AI answers, so a link nobody here
+  // wrote must never be able to blank the page. An unknown id scrolls to top.
   useEffect(() => {
-    if (hash) {
-      const el = document.querySelector(hash)
+    if (hash.length > 1) {
+      let el = null
+      try {
+        el = document.getElementById(decodeURIComponent(hash.slice(1)))
+      } catch {
+        el = null // a fragment that is not valid percent-encoding
+      }
       if (el) {
         el.scrollIntoView({ behavior: 'smooth' })
         return