html fixes

frontend/index.html

@@ -120,10 +120,12 @@
     </table>
     <br>
     <table class="table">
-      <th class="thead-dark">
-        <td>Parameter</td>
-        <td>Value</td>
-      </th>
+      <thead class="thead-dark">
+        <tr>
+          <th>Parameter</th>
+          <th>Value</th>
+        </tr>
+      </thead>
       <tr>
         <td>Illuminance [lx]</td>
         <td id="lx">---</td>