Ramoonus

This plugin adds the Modernizr to your WordPress installation. 
Modernizr is a small JavaScript library that detects the availability of native implementations for next-generation web technologies, i.e. features that stem from the HTML5 and CSS3 specifications. Many of these features are already implemented in at least one major browser (most of them in two or more), and what Modernizr does is, very simply, tell you whether the current browser has this feature natively implemented or not.
For documentation visit http://www.modernizr.com/docs/

Modernizr for WordPress

The 2.8.4 version inserts broken javascript link. I posted a message about this in the support section for the plugin and the author has not responded or fixed the problem. Now, any site that I've added this plugin to can be broken if the user runs an update. 

Instead, if you need Modernizr, insert the following into your header.php file just after <?php wp_head(); ?>:

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/modernizr/2.8.3/modernizr.min.js"></script>

Doesn't work - Plugin Defunct

This plugin adds the Modernizr to your WordPress installation.

SirZooro

mrodrigow

This plugin detects if visitor is using the OLD Internet Explorer 6 (or even older) and displays a message to him to download a better browser, or at least upgrade to a new version of IE.
This plugin supports the languages
<ul>
<li>English</li>
<li>Portuguese Brazil</li>
<li>Turkish (thanks to <a href="http://www.gezi-yorum.net/" title="Jackoon" rel="nofollow ugc">Jackoon</a>)</li>
<li>Spanish (thanks to <a href="http://www.segmentationfault.es/" title="tbhot3ww" rel="nofollow ugc">tbhot3ww</a>)</li>
<li>Polish (thanks to <a href="http://blog.poradnik-webmastera.com/" title="SirZooro" rel="nofollow ugc">SirZooro</a>)</li>
<li>Dutch (thanks to Johandm8)</li>
<li>Italian (thanks to <a href="http://linuxbox360.org/" title="NitroRabber" rel="nofollow ugc">NitroRabber</a>)</li>
<li>German (thanks to <a href="http://cedric-wetzel.eu" title="Cedric Wetzel" rel="nofollow ugc">Cedric Wetzel</a> and 
<a href="http://www.wick0r.de/" title="Wick0r" rel="nofollow ugc">Wick0r</a>)</li>
<li>Russian (thanks to <a href="http://www.fatcow.com/" title="Fat Cow" rel="nofollow ugc">Fat Cow</a>)</li>
<li>Belorusian (thanks to <a href="http://antsar.info/" title="ilyuha" rel="nofollow ugc">ilyuha</a>)</li>
<li>Czech (thanks to <a href="http://raduzdesign.com/" title="Radek Stangel" rel="nofollow ugc">Radek Stangel</a>)</li>
</ul>
If you like it, donate 2 seconds rating this plugin 🙂
Comments at <a href="http://marcelorodrigo.com/wordpress-plugins/internet-explorer-6-upgrade" title="my Blog" rel="nofollow ugc">my Blog</a> are welcome! 
If your language not here, please translate and <a href="http://marcelorodrigo.com/wordpress-plugins/internet-explorer-6-upgrade" title="send to us" rel="nofollow ugc">send to us</a>. Your language will be added in the next version!

Internet Explorer 6 Upgrade

Detects if visitor using Internet Explorer 6 and offers a screen to download a better an update version of most popular browsers

Modernizr for WordPress vs Internet Explorer 6 Upgrade