fix forward links in doc example

doc/index.html

@@ -97,7 +97,7 @@ <h2 id="example">Examples</h2>
     <pre>(toplevel-tk)</pre>
 
     <p>This will automatically create a suitable Tk back-end. See <a
-    href="#backends">below</a> for details on what these back-ends
+    href="#back-ends">below</a> for details on what these back-ends
     are.</p>
 
     <p>You should now see an empty window. Next, we'll want to put
@@ -110,7 +110,7 @@ <h2 id="example">Examples</h2>
 
     <pre>(tcl "pack" (tcl[ "ttk::label" ".label" :text "Hello world"))</pre>
 
-    <p>See <a href="#conversion">below</a> for information about the
+    <p>See the <a href="#tcl">reference</a> for information about the
     way in which arguments to <a href="#tcl"><code>tcl</code></a> and
     <a href="#tcl_"><code>tcl[</code></a> are treated.</p>