Bug 315525 Document new tab behaviour under Win when starting SM with an instance already running. r=iann_bugzilla

extensions/help/resources/locale/en-US/cs_nav_prefs_navigator.xhtml

@@ -479,6 +479,25 @@
   </li>
 </ul>
 
+<div class="win">
+  <p>To ensure that &brandShortName; opens a new window, select the Navigator
+    option in <a href= "cs_nav_prefs_appearance.xhtml#appearance>Appearance
+    Preferences - Appearance</a>.</p>
+
+  <p>If you want &brandShortName; to open a new tab instead of a new window when
+    you launch it and it is already running, ensure the following:
+
+  <ul>
+    <li>If you launch &brandShortName; by command line, do not use command-line
+      parameters that open windows.</li>
+    <li>Nothing is set in the
+      <a href= "cs_nav_prefs_appearance.xhtml#appearance>Appearance Preferences
+      - Appearance</a>.</li>
+    <li>Set <q>Links from other applications</q> preference to <q>A new tab in
+      the current window</q>.</li>
+  </ul>
+</div>
+
 <p>[<a href="#navigator_preferences">Return to beginning of section</a>]</p>
 
 <h2 id="downloads">Navigator Preferences - Downloads</h2>