README: Documented scheme for header identifiers in HTML.

git-svn-id: https://pandoc.googlecode.com/svn/trunk@680 788f1e2b-df1e-0410-8736-df70ead52e1b

README

@@ -597,40 +597,6 @@ These work like simple tables, but with the following differences:
   - They must end with a row of dashes, then a blank line.
   - The rows must be separated by blank lines. 
 
-Embedded HTML
--------------
-
-Pandoc treats embedded HTML in markdown a bit differently than
-Markdown 1.0.  While Markdown 1.0 leaves HTML blocks exactly as they
-are, Pandoc treats text between HTML tags as markdown.  Thus, for
-example, Pandoc will turn
-
-	<table>
-		<tr>
-			<td>*one*</td>
-			<td>[a link](http://google.com)</td>
-		</tr>
-	</table>
-
-into
-
-	<table>
-		<tr>
-			<td><em>one</em></td>
-			<td><a href="http://google.com">a link</a></td>
-		</tr>
-	</table>
-
-whereas `Markdown.pl` will preserve it as is.
-
-There is one exception to this rule:  text between `<script>` and
-`</script>` tags is not interpreted as markdown.
-
-This departure from standard markdown should make it easier to mix
-markdown with HTML block elements.  For example, one can surround
-a block of markdown text with `<div>` tags without preventing it
-from being interpreted as markdown.
-
 Title blocks
 ------------
 
@@ -675,6 +641,75 @@ For example,
 
 The middle of the man page footer is used for the date.
 
+Markdown in HTML blocks
+-----------------------
+
+While standard markdown leaves HTML blocks exactly as they are, Pandoc
+treats text between HTML tags as markdown. Thus, for example, Pandoc
+will turn
+
+	<table>
+		<tr>
+			<td>*one*</td>
+			<td>[a link](http://google.com)</td>
+		</tr>
+	</table>
+
+into
+
+	<table>
+		<tr>
+			<td><em>one</em></td>
+			<td><a href="http://google.com">a link</a></td>
+		</tr>
+	</table>
+
+whereas `Markdown.pl` will preserve it as is.
+
+There is one exception to this rule:  text between `<script>` and
+`</script>` tags is not interpreted as markdown.
+
+This departure from standard markdown should make it easier to mix
+markdown with HTML block elements.  For example, one can surround
+a block of markdown text with `<div>` tags without preventing it
+from being interpreted as markdown.
+
+Header identifiers in HTML
+--------------------------
+
+Each header element in pandoc's HTML output is given a unique
+identifier. This identifier is based on the text of the header. To
+derive the identifier from the header text,
+
+  - Remove all formatting, links, etc.
+  - Remove all punctuation, except dashes and hyphens.
+  - Replace all spaces, dashes, newlines, and hyphens with hyphens.
+  - Convert all alphabetic characters to lowercase.
+
+Thus,
+
+                         Header text     Identifier
+   --------------------------------- --- ----------------------------
+         Header identifiers in HTML   →  `header-identifiers-in-html`
+             *Dogs*?--in *my* house?  →  `dogs--in-my-house`
+             [HTML], [S5], or [RTF]?  →  `html-s5-or-rtf`
+
+These rules should, in most cases, allow one to determine the identifier
+from the header text. The exception is when several headers have the
+same text; in this case, the first will get an identifier as described
+above; the second will get the same identifier with `-1` appended; the
+third with `-2`; and so on.
+
+These identifiers are used to provide link targets in the table of
+contents generated by the `--toc|--table-of-contents` option. They
+also make it easy to provide links from one section of a document to
+another. A link to this section, for example, might look like this:
+
+    See the section on [header identifiers](#header-identifiers-in-html). 
+
+Note, however, that this method of providing links to sections works
+only in HTML.
+
 Box-style blockquotes
 ---------------------