diff --git a/documentation/optimization.html b/documentation/optimization.html
index d6867b1870..84fb71dcb7 100755
--- a/documentation/optimization.html
+++ b/documentation/optimization.html
@@ -406,9 +406,9 @@ Header append Vary User-Agent env=!dont-vary
 </pre>
 <hr />
 Don't have time or resources to optimize your Chamilo installation yourself? Hire an <a href="http://www.chamilo.org/en/providers">official Chamilo provider</a> and get it sorted out professionally by specialists.
-    <a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-xhtml10-blue" alt="Valid XHTML 1.0 Transitional" style="margin: 1em; float: right;" height="31" width="88" /></a>
+    <a href="http://validator.w3.org/check?uri=referer"><img src="//www.w3.org/Icons/valid-xhtml10-blue" alt="Valid XHTML 1.0 Transitional" style="margin: 1em; float: right;" height="31" width="88" /></a>
 	<a href="http://jigsaw.w3.org/css-validator/">
-		<img src="http://jigsaw.w3.org/css-validator/images/vcss-blue" style="margin: 1em; float: right;" alt="Valid CSS" />
+		<img src="//jigsaw.w3.org/css-validator/images/vcss-blue" style="margin: 1em; float: right;" alt="Valid CSS" />
 	</a>
 <hr />
 
@@ -604,10 +604,10 @@ This should have an immediate effect on the load average on your server.
 </ul>
 <hr />
 Don't have time or resources to optimize your Chamilo installation
-    yourself? Hire an <a href="http://www.chamilo.org/en/providers">official Chamilo provider</a> and get it sorted out professionally by specialists.
-    <a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-xhtml10-blue" alt="Valid XHTML 1.0 Transitional" style="margin: 1em; float: right;" height="31" width="88" /></a>
+    yourself? Hire an <a href="//www.chamilo.org/en/providers">official Chamilo provider</a> and get it sorted out professionally by specialists.
+    <a href="http://validator.w3.org/check?uri=referer"><img src="//www.w3.org/Icons/valid-xhtml10-blue" alt="Valid XHTML 1.0 Transitional" style="margin: 1em; float: right;" height="31" width="88" /></a>
 	<a href="http://jigsaw.w3.org/css-validator/">
-		<img src="http://jigsaw.w3.org/css-validator/images/vcss-blue" style="margin: 1em; float: right;" alt="Valid CSS" />
+		<img src="//jigsaw.w3.org/css-validator/images/vcss-blue" style="margin: 1em; float: right;" alt="Valid CSS" />
 	</a>
 </div>
 </body>