diff --git a/index.html b/index.html
index 4831274..f18f390 100644
--- a/index.html
+++ b/index.html
@@ -349,6 +349,11 @@ <h3>
         is 1000 milliseconds long (i.e., don't account for leap seconds).
         </li>
       </ol>
+      <p class="note">
+        A {{DOMHighResTimeStamp}} is a double. Therefore, using it to represent an
+        [=epoch-relative timestamp=], e.g. for the purpose of comparing it with <a>Date.now()</a>,
+        might lose sub-millisecond precision.
+        </p>
     </section>
     <section id="sec-domhighrestimestamp">
       <h3>