Update PNG reference.

Author: dbaron

css3-color/Overview.html

@@ -498,8 +498,8 @@ <h3 id=foreground><span class=secno>3.1 </span>Foreground color: the <span
   <h4 id=gamma><span class=secno>3.1.1 </span>Gamma correction</h4>
 
   <p><em>For information about gamma issues, please consult the Gamma
-   Tutorial in the PNG specification (<a href="#PNG1.0"
-   rel=biblioentry>[PNG1.0]<!--{{!PNG1.0}}--></a>).</em>
+   Tutorial in the PNG specification (<a href="#PNG2e"
+   rel=biblioentry>[PNG2e]<!--{{!PNG2e}}--></a>).</em>
 
   <p> In the computation of gamma correction, UAs displaying on a <abbr
    title="cathode ray tube">CRT</abbr> may assume an ideal CRT and ignore any
@@ -4853,11 +4853,13 @@ <h3 id=normative><span class=secno>11.1 </span>Normative</h3>
     </dd>
    <!---->
 
-   <dt id=PNG1.0>[PNG1.0]
+   <dt id=PNG2e>[PNG2e]
 
-   <dd>T. Boutell (ed). <cite>PNG (Portable Network Graphics) Specification,
-    Version 1.0.</cite> 1 October 1996. W3C Recommendation. URL: <a
-    href="http://www.w3.org/TR/REC-png-multi.html">http://www.w3.org/TR/REC-png-multi.html</a>
+   <dd>David Duce (ed). <cite>Portable Network Graphics (PNG) Specification
+    (Second Edition).</cite> 10 November 2003. W3C Recommendation &amp;
+    ISO/IEC International Standard 15948:2003. Including later updates URL:
+    <a
+    href="http://www.w3.org/TR/2003/REC-PNG-20031110">http://www.w3.org/TR/2003/REC-PNG-20031110</a>
     </dd>
    <!---->
 

css3-color/Overview.src.html

@@ -318,7 +318,7 @@ <h3 id="foreground">Foreground color: the <span class="property">'color'</span>
 <h4 id="gamma">Gamma correction</h4>
 
 <p><em>For information about gamma issues, please consult the
-Gamma Tutorial in the PNG specification ([[!PNG1.0]]).</em></p>
+Gamma Tutorial in the PNG specification ([[!PNG2e]]).</em></p>
 
 <p> In the computation of gamma correction, UAs displaying on a <abbr title="cathode ray tube">CRT</abbr>
 may assume an ideal CRT and ignore any effects on apparent gamma