fixes #11961: dropdown alignment docs improvements

components.html

@@ -107,8 +107,12 @@ base_url: "../"
 </div>
 {% endhighlight %}
 
-    <h3 id="dropdowns-alignment">Alignment options</h3>
-    <p>Add <code>.dropdown-menu-right</code> to a <code>.dropdown-menu</code> to right align the dropdown menu.</p>
+    <h3 id="dropdowns-alignment">Alignment</h3>
+    <p>By default, a dropdown menu is automatically positioned 100% from the top and along the left side of its parent. Add <code>.dropdown-menu-right</code> to a <code>.dropdown-menu</code> to right align the dropdown menu.</p>
+    <div class="bs-callout bs-callout-warning">
+      <h4>May require additional positioning</h4>
+      <p>Dropdowns are automatically positioned via CSS within the normal flow of the document. This means dropdowns may be cropped by parents with certain <code>overflow</code> properties or appear out of bounds of the viewport. Address these issues on your own as they arise.</p>
+    </div>
     <div class="bs-callout bs-callout-warning">
       <h4>Deprecated <code>.pull-right</code> alignment</h4>
       <p>As of v3.1, we've deprecated <code>.pull-right</code> on dropdown menus. To right-align a menu, use <code>.dropdown-menu-right</code>. Right-aligned nav components in the navbar use a mixin version of this class to automatically align the menu. To override it, use <code>.dropdown-menu-left</code>.</p>