Merged [2976] from lars.eggert@nokia.com:

Remove unused images. Convert GIFs to smaller PNGs.
Optimize all images with http://www.smushit.com/ysmush.it/
 - Legacy-Id: 2979
Note: SVN reference [2976] has been migrated to Git commit 92b7e87

Author: levkowetz

ietf/templates/404.html

@@ -3,7 +3,7 @@
 {% block title %}404 Not Found{% endblock %}
 {% block content %}
 
-<img src="/images/ietflogo2e.gif" height="80" width="140"/>
+<img src="/images/ietflogo2e.png" height="80" width="140"/>
 
 <h2>The page you were looking for couldn't be found.</h2>
 

ietf/templates/500.html

@@ -3,7 +3,7 @@
 {% block title %}500 Internal Server Error{% endblock %}
 {% block content %}
 
-<img src="/images/ietflogo2e.gif" height="80" width="140">
+<img src="/images/ietflogo2e.png" height="80" width="140">
 
 <h2>Internal Server Error.</h2>
 

ietf/templates/idrfc/main.html

@@ -49,7 +49,7 @@
 <table>
 <tr valign="middle">
 <td colspan="2" class="ietf-main-title"><h1>IETF Datatracker</h1></td>
-<td class="ietf-main-logo"><div><img src="/images/ietflogo.gif" width="140" alt=""/></div></td>
+<td class="ietf-main-logo"><div><img src="/images/ietflogo.png" width="140" alt=""/></div></td>
 </tr>
 
 <tr valign="top"><td class="ietf-box ietf-main-search">

ietf/templates/idtracker/states.html

@@ -7,7 +7,7 @@
 
    <h1>Main I-D States</h1>
 
-<p><a href="/images/state_diagram.gif">View Diagram</a></p>
+<p><a href="/images/state_diagram.png">View Diagram</a></p>
 
    <table class="ietf-table">