Use protocol-relative URL

serendipity_event_geotag/plugin_version.inc.php

@@ -1,5 +1,5 @@
 <?php
 
 // Actual version of both plugins
-@define('PLUGIN_EVENT_GEOTAG_VERSION',	'1.33.2');
+@define('PLUGIN_EVENT_GEOTAG_VERSION',	'1.33.3');
 @define('PLUGIN_EVENT_GEOTAG_AUTHOR', 	'Zoran Kovacevic, Grischa Brockhaus, Matthias Gutjahr');

serendipity_event_geotag/serendipity_plugin_geotag.php

@@ -356,7 +356,7 @@ xmlhttp.send(null);
 
         } elseif ($service === 'osm') {
             ?>
-<script src="http://openlayers.org/api/OpenLayers.js"></script>
+<script src="//openlayers.org/api/OpenLayers.js"></script>
 <script type="text/javascript">
 (function () {
     createPopup = function (evt) {