Index: test/unit/helpers/application_helper_test.rb
===================================================================
--- test/unit/helpers/application_helper_test.rb	(revision 2845)
+++ test/unit/helpers/application_helper_test.rb	(working copy)
@@ -304,7 +304,7 @@
   end

   def test_table_of_content
-    raw = <<-RAW
+    raw = <<-'RAW'
 {{toc}}

 h1. Title
@@ -321,14 +321,23 @@

 h1. Another title

+h2. Subtitle with x%x% redcloth3 dummy character
+
+h2. Subtitle with "#$%'()*+,-./:;<=>?@[\]^_{|}~ incorrect characters
+
+h2. Subtitle with russian character "абв" (utf8)
+
 RAW

     expected = '<ul class="toc">' +
-               '<li class="heading1"><a href="#Title">Title</a></li>' +
-               '<li class="heading2"><a href="#Subtitle-with-a-Wiki-link">Subtitle with a Wiki link</a></li>' +
-               '<li class="heading2"><a href="#Subtitle-with-another-Wiki-link">Subtitle with another Wiki link</a></li>' +
-               '<li class="heading2"><a href="#Subtitle-with-red-text">Subtitle with red text</a></li>' +
-               '<li class="heading1"><a href="#Another-title">Another title</a></li>' +
+               '<li class="heading1"><a href="#h-Title">Title</a></li>' +
+               '<li class="heading2"><a href="#h-Subtitle-with-a-Wiki-link">Subtitle with a Wiki link</a></li>' +
+               '<li class="heading2"><a href="#h-Subtitle-with-another-Wiki-link">Subtitle with another Wiki link</a></li>' +
+               '<li class="heading2"><a href="#h-Subtitle-with-red-text">Subtitle with red text</a></li>' +
+               '<li class="heading1"><a href="#h-Another-title">Another title</a></li>' +
+               '<li class="heading2"><a href="#h-Subtitle-with-redcloth3-dummy-character">Subtitle with &#38; redcloth3 dummy character</a></li>' +
+               '<li class="heading2"><a href="#h-Subtitle-with-incorrect-characters">Subtitle with "#$%\'()*+,-./:;<=>?@[\]^_{|}~ incorrect characters</a></li>' +
+               '<li class="heading2"><a href="#h-Subtitle-with-russian-character-.D0.B0.D0.B1.D0.B2-utf8">Subtitle with russian character "абв" (utf8)</a></li>' +
                '</ul>'

     assert textilizable(raw).gsub("\n", "").include?(expected)
Index: lib/redmine/wiki_formatting/textile/formatter.rb
===================================================================
--- lib/redmine/wiki_formatting/textile/formatter.rb	(revision 2845)
+++ lib/redmine/wiki_formatting/textile/formatter.rb	(working copy)
@@ -66,13 +66,21 @@
         def textile_p_withtoc(tag, atts, cite, content)
           # removes wiki links from the item
           toc_item = content.gsub(/(\[\[([^\]\|]*)(\|([^\]]*))?\]\])/) { $4 || $2 }
+
           # removes styles
           # eg. %{color:red}Triggers% => Triggers
           toc_item.gsub! %r[%\{[^\}]*\}([^%]+)%], '\\1'

-          # replaces non word caracters by dashes
-          anchor = toc_item.gsub(%r{[^\w\s\-]}, '').gsub(%r{\s+(\-+\s*)?}, '-')
+          # removes all except the alphabet, digits, hyphens
+          # and dummy character of incoming ampersand (see redcloth3)
+          # for compatibility with rfc952, also replace space and repeatable hyphens
+          anchor = toc_item.gsub(%r{[^\w\s\-]|_|(x\%x\%)}, '').gsub(%r{\s+(\-+\s*)?}, '-')

+          # ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed
+          # by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"),
+          # colons (":"), and periods ("."). (http://www.w3.org/TR/html4/types.html#h-6.2)
+          anchor = 'h-' + CGI.escape(anchor).gsub('%', '.')
+
           unless anchor.blank?
             if tag =~ /^h(\d)$/
               @toc << [$1.to_i, anchor, toc_item]