added reload note

sd-card/html/ota_page.html

@@ -37,6 +37,7 @@ web interface (<i><span style="font-family:monospace">html__*.zip</span></i>). H
     web interface at the same time!</p>
 <hr>
 <h2>Update</h2>
+<b>Do not reload the page or switch to another page while the update is in progress!</b>
 <table class="fixed" border="0">
     <tr>
         <p>