Fix UI layout in sync modes

code/html/index.html

@@ -320,7 +320,7 @@
 
                                 <div class="pure-g module module-multirelay">
                                     <label class="pure-u-1 pure-u-lg-1-4">Switch sync mode</label>
-                                    <select name="relaySync" class="pure-u-1 pure-u-3-4" tabindex="3">
+                                    <select name="relaySync" class="pure-u-1 pure-u-lg-3-4" tabindex="3">
                                         <option value="0">No synchonisation</option>
                                         <option value="1">Zero or one switches active</option>
                                         <option value="2">One and just one switch active</option>