Add missing dot

www/index.html

@@ -234,7 +234,7 @@ <h5 class="card-subtitle mb-2 text-muted">How much time has passed since the las
 
             <p class="card-text">
               The time displayed in the chart is the time the blocks arrived over the
-              <abbr title="While blocks contain a timestamp field in the block header, this timestamp must not be the time the block was actually mined. Thus this timestamp is not useful for this chart.">P2P network</abbr>
+              <abbr title="While blocks contain a timestamp field in the block header, this timestamp must not be the time the block was actually mined. Thus this timestamp is not useful for this chart.">P2P network</abbr>.
               Hovering over a block shows additional information like the transaction count and the block size.
               The time since the last block is marked red.              
             </p>