diff --git a/src/calibre/gui2/tweak_book/boss.py b/src/calibre/gui2/tweak_book/boss.py
index 4e5beed957..15b8e39c20 100644
--- a/src/calibre/gui2/tweak_book/boss.py
+++ b/src/calibre/gui2/tweak_book/boss.py
@@ -228,6 +228,7 @@ class Boss(QObject):
         for name in tuple(editors):
             self.close_editor(name)
         self.gui.preview.clear()
+        self.gui.live_css.clear()
         self.container_count = -1
         if self.tdir:
             shutil.rmtree(self.tdir, ignore_errors=True)
@@ -311,6 +312,7 @@ class Boss(QObject):
                 self.close_editor(name)
         if not editors:
             self.gui.preview.clear()
+            self.gui.live_css.clear()
         if remove_names_from_toc(current_container(), spine_names + list(other_items)):
             self.gui.toc_view.update_if_visible()
             toc = find_existing_toc(current_container())
@@ -1028,11 +1030,19 @@ class Boss(QObject):
             if name is not None and getattr(ed, 'syntax', None) == 'html':
                 self.gui.preview.sync_to_editor(name, ed.current_line)
 
+    def sync_live_css_to_editor(self):
+        ed = self.gui.central.current_editor
+        if ed is not None:
+            name = editor_name(ed)
+            if name is not None and getattr(ed, 'syntax', None) == 'html':
+                self.gui.live_css.sync_to_editor(name)
+
     def init_editor(self, name, editor, data=None, use_template=False):
         editor.undo_redo_state_changed.connect(self.editor_undo_redo_state_changed)
         editor.data_changed.connect(self.editor_data_changed)
         editor.copy_available_state_changed.connect(self.editor_copy_available_state_changed)
         editor.cursor_position_changed.connect(self.sync_preview_to_editor)
+        editor.cursor_position_changed.connect(self.sync_live_css_to_editor)
         editor.cursor_position_changed.connect(self.update_cursor_position)
         if hasattr(editor, 'word_ignored'):
             editor.word_ignored.connect(self.word_ignored)
@@ -1153,6 +1163,7 @@ class Boss(QObject):
                     # focused. This is not inefficient since multiple requests
                     # to sync are de-bounced with a 100 msec wait.
                     self.sync_preview_to_editor()
+                self.sync_live_css_to_editor()
             if name is not None:
                 self.gui.file_list.mark_name_as_current(name)
             if ed.has_line_numbers:
@@ -1182,6 +1193,7 @@ class Boss(QObject):
         editor.break_cycles()
         if not editors or getattr(self.gui.central.current_editor, 'syntax', None) != 'html':
             self.gui.preview.clear()
+            self.gui.live_css.clear()
 
     def insert_character(self):
         self.gui.insert_char.show()
@@ -1251,6 +1263,7 @@ class Boss(QObject):
 
     def shutdown(self):
         self.gui.preview.stop_refresh_timer()
+        self.gui.live_css.stop_update_timer()
         self.save_state()
         [x.reject() for x in _diff_dialogs]
         del _diff_dialogs[:]
diff --git a/src/calibre/gui2/tweak_book/editor/smart/__init__.py b/src/calibre/gui2/tweak_book/editor/smart/__init__.py
index b5f54e5ccb..7b5352d78c 100644
--- a/src/calibre/gui2/tweak_book/editor/smart/__init__.py
+++ b/src/calibre/gui2/tweak_book/editor/smart/__init__.py
@@ -20,3 +20,6 @@ class NullSmarts(object):
     def verify_for_spellcheck(self, cursor, highlighter):
         return False
 
+    def cursor_position_with_sourceline(self, cursor):
+        return None, None
+
diff --git a/src/calibre/gui2/tweak_book/editor/smart/html.py b/src/calibre/gui2/tweak_book/editor/smart/html.py
index 243beb7bd8..9ffe7ea697 100644
--- a/src/calibre/gui2/tweak_book/editor/smart/html.py
+++ b/src/calibre/gui2/tweak_book/editor/smart/html.py
@@ -312,3 +312,26 @@ class HTMLSmarts(NullSmarts):
 
         return False
 
+    def cursor_position_with_sourceline(self, cursor):
+        ''' Return the tag containing the current cursor as a source line
+        number and a list of tags defined on that line upto and including the
+        containing tag. '''
+        block = cursor.block()
+        offset = cursor.position() - block.position()
+        block, boundary = next_tag_boundary(block, offset, forward=False)
+        if block is None:
+            return None, None
+        if boundary.is_start:
+            # We are inside a tag, use this tag
+            start_block, start_offset = block, boundary.offset
+        else:
+            tag = find_closest_containing_tag(block, offset)
+            if tag is None:
+                return None, None
+            start_block, start_offset = tag.start_block, tag.start_offset
+        sourceline = start_block.blockNumber()
+        ud = start_block.userData()
+        if ud is None:
+            return None, None
+        all_tags = [t.name for t in ud.tags if (t.is_start and not t.closing and t.offset <= start_offset)]
+        return sourceline, all_tags
diff --git a/src/calibre/gui2/tweak_book/editor/text.py b/src/calibre/gui2/tweak_book/editor/text.py
index 96cf4d5b1b..a7ab7c02c6 100644
--- a/src/calibre/gui2/tweak_book/editor/text.py
+++ b/src/calibre/gui2/tweak_book/editor/text.py
@@ -749,3 +749,6 @@ class TextEdit(PlainTextEdit):
         if hasattr(self.smarts, 'rename_block_tag'):
             self.smarts.rename_block_tag(self, new_name)
 
+    def current_tag(self):
+        return self.smarts.cursor_position_with_sourceline(self.textCursor())
+
diff --git a/src/calibre/gui2/tweak_book/editor/widget.py b/src/calibre/gui2/tweak_book/editor/widget.py
index 4e9cdfd53a..a60e1418a8 100644
--- a/src/calibre/gui2/tweak_book/editor/widget.py
+++ b/src/calibre/gui2/tweak_book/editor/widget.py
@@ -112,6 +112,9 @@ class Editor(QMainWindow):
             self.editor.go_to_line(val)
         return property(fget=fget, fset=fset)
 
+    def current_tag(self):
+        return self.editor.current_tag()
+
     @property
     def number_of_lines(self):
         return self.editor.blockCount()
diff --git a/src/calibre/gui2/tweak_book/live_css.py b/src/calibre/gui2/tweak_book/live_css.py
new file mode 100644
index 0000000000..74e1f526f6
--- /dev/null
+++ b/src/calibre/gui2/tweak_book/live_css.py
@@ -0,0 +1,65 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__ = 'GPL v3'
+__copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
+
+from PyQt4.Qt import (QWidget, QTimer)
+
+from calibre.gui2.tweak_book import editors, actions
+
+class LiveCSS(QWidget):
+
+    def __init__(self, preview, parent=None):
+        QWidget.__init__(self, parent)
+        self.preview = preview
+        preview.refreshed.connect(self.update_data)
+        self.update_timer = QTimer(self)
+        self.update_timer.timeout.connect(self.update_data)
+        self.update_timer.setSingleShot(True)
+
+    def clear(self):
+        pass  # TODO: Implement this
+
+    def show_data(self, editor_name, sourceline, tags):
+        if sourceline is None:
+            self.clear()
+        else:
+            pass  # TODO: Do update
+
+    @property
+    def current_name(self):
+        return self.preview.current_name
+
+    @property
+    def is_visible(self):
+        return self.isVisible()
+
+    def showEvent(self, ev):
+        self.update_timer.start()
+        actions['auto-reload-preview'].setEnabled(True)
+        return QWidget.showEvent(self, ev)
+
+    def sync_to_editor(self, name):
+        self.start_update_timer()
+
+    def update_data(self):
+        if not self.is_visible:
+            return
+        editor_name = self.current_name
+        ed = editors.get(editor_name, None)
+        if self.update_timer.isActive() or (ed is None and editor_name is not None):
+            return QTimer.singleShot(100, self.update_data)
+        if ed is not None:
+            sourceline, tags = ed.current_tag()
+            self.show_data(editor_name, sourceline, tags)
+
+    def start_update_timer(self):
+        if self.is_visible:
+            self.update_timer.start(1000)
+
+    def stop_update_timer(self):
+        self.update_timer.stop()
+
diff --git a/src/calibre/gui2/tweak_book/preview.py b/src/calibre/gui2/tweak_book/preview.py
index 876033545b..5e0c7fb11f 100644
--- a/src/calibre/gui2/tweak_book/preview.py
+++ b/src/calibre/gui2/tweak_book/preview.py
@@ -435,6 +435,7 @@ class Preview(QWidget):
     split_requested = pyqtSignal(object, object, object)
     split_start_requested = pyqtSignal()
     link_clicked = pyqtSignal(object, object)
+    refreshed = pyqtSignal()
 
     def __init__(self, parent=None):
         QWidget.__init__(self, parent)
@@ -558,6 +559,7 @@ class Preview(QWidget):
                 self.view.setUrl(current_url)
             else:
                 self.view.refresh()
+            self.refreshed.emit()
 
     def clear(self):
         self.view.clear()
@@ -567,14 +569,26 @@ class Preview(QWidget):
     def is_visible(self):
         return actions['preview-dock'].isChecked()
 
+    @property
+    def live_css_is_visible(self):
+        try:
+            return actions['live-css-dock'].isChecked()
+        except KeyError:
+            return False
+
     def start_refresh_timer(self):
-        if self.is_visible and actions['auto-reload-preview'].isChecked():
+        if self.live_css_is_visible or (self.is_visible and actions['auto-reload-preview'].isChecked()):
             self.refresh_timer.start(tprefs['preview_refresh_time'] * 1000)
 
     def stop_refresh_timer(self):
         self.refresh_timer.stop()
 
     def auto_reload_toggled(self, checked):
+        if self.live_css_is_visible and not actions['auto-reload-preview'].isChecked():
+            actions['auto-reload-preview'].setChecked(True)
+            error_dialog(self, _('Cannot disable'), _(
+                'Auto reloading of the preview panel cannot be disabled while the'
+                ' Live CSS panel is open.'), show=True)
         actions['auto-reload-preview'].setToolTip(_(
             'Auto reload preview when text changes in editor') if not checked else _(
                 'Disable auto reload of preview'))
diff --git a/src/calibre/gui2/tweak_book/ui.py b/src/calibre/gui2/tweak_book/ui.py
index c43084f54c..e882d78bf0 100644
--- a/src/calibre/gui2/tweak_book/ui.py
+++ b/src/calibre/gui2/tweak_book/ui.py
@@ -33,6 +33,7 @@ from calibre.gui2.tweak_book.spell import SpellCheck
 from calibre.gui2.tweak_book.search import SavedSearches
 from calibre.gui2.tweak_book.toc import TOCViewer
 from calibre.gui2.tweak_book.char_select import CharSelect
+from calibre.gui2.tweak_book.live_css import LiveCSS
 from calibre.gui2.tweak_book.editor.widget import register_text_editor_actions
 from calibre.gui2.tweak_book.editor.insert_resource import InsertImage
 from calibre.utils.icu import character_name
@@ -595,6 +596,13 @@ class Main(MainWindow):
         d.setWidget(self.preview)
         self.addDockWidget(Qt.RightDockWidgetArea, d)
 
+        d = create(_('Live CSS'), 'live-css')
+        d.setAllowedAreas(Qt.LeftDockWidgetArea | Qt.RightDockWidgetArea | Qt.BottomDockWidgetArea | Qt.TopDockWidgetArea)
+        self.live_css = LiveCSS(self.preview, parent=d)
+        d.setWidget(self.live_css)
+        self.addDockWidget(Qt.RightDockWidgetArea, d)
+        d.close()  # Hidden by default
+
         d = create(_('Check Book'), 'check-book')
         d.setAllowedAreas(Qt.LeftDockWidgetArea | Qt.RightDockWidgetArea | Qt.BottomDockWidgetArea | Qt.TopDockWidgetArea)
         d.setWidget(self.check_book)