diff --git a/src/pyj/read_book/iframe.pyj b/src/pyj/read_book/iframe.pyj
index 328a175550..3f10483545 100644
--- a/src/pyj/read_book/iframe.pyj
+++ b/src/pyj/read_book/iframe.pyj
@@ -251,6 +251,7 @@ class IframeBoss:
         document.documentElement.style.overflow = 'hidden'
         if self.is_titlepage and not opts.cover_preserve_aspect_ratio:
             document.body.classList.add('cover-fill')
+        document.body.classList.add(f'calibre-viewer-{window.navigator.epubReadingSystem.layoutStyle}')
         self.last_window_width, self.last_window_height = scroll_viewport.width(), scroll_viewport.height()
         apply_settings()
         self.fix_fullscreen_svg_images()
diff --git a/src/pyj/read_book/prefs/user_stylesheet.pyj b/src/pyj/read_book/prefs/user_stylesheet.pyj
index b51dbfdd31..24be315e00 100644
--- a/src/pyj/read_book/prefs/user_stylesheet.pyj
+++ b/src/pyj/read_book/prefs/user_stylesheet.pyj
@@ -103,9 +103,12 @@ def create_user_stylesheet_panel(container, apply_func, cancel_func):
                     _('A CSS style sheet that can be used to control the look and feel of the text. For examples, click'), ' ',
                     E.a(class_='blue-link', title=_("Examples of user style sheets"),
                         target=('_self' if runtime.is_standalone_viewer else '_blank'),
-                        href='https://www.mobileread.com/forums/showthread.php?t=51500', _('here'))
+                        href='https://www.mobileread.com/forums/showthread.php?t=51500', _('here.')),
+                    ' ', _(
+                        'Note that you can use the selectors body.calibre-viewer-paginated and body.calibre-viewer-scrolling'
+                        ' to target the Paged and Flow modes.')
                 ),
-                E.textarea(name='user-stylesheet', style='width: 100%; margin-top: 1ex; box-sizing: border-box; flex-grow: 10')
+                E.textarea(name='user-stylesheet', style='width: 100%; margin-top: 1ex; box-sizing: border-box; flex-grow: 10'),
             )
         )
     )