// Improved label of IETF language tag

admin-dev/themes/default/css/admin.css

@@ -25,6 +25,9 @@ select[disabled="disabled"], input[disabled="disabled"],textarea[disabled="disab
 .double_select select{width:300px;height:160px;}
 .double_select a{text-align:center;display:block;border:1px solid #aaa;text-decoration:none;background-color:#fafafa;color:#123456;margin:2px;padding:2px}
 
+.icon {vertical-align:middle}
+.icon-top {vertical-align:top}
+
 /*BUTTON*/
 .button{
 	background: #e3e3e3 url('../img/bg-button-degrade.png') repeat-x scroll left top;

controllers/admin/AdminLanguagesController.php

@@ -144,7 +144,7 @@ class AdminLanguagesControllerCore extends AdminController
 					'required' => true,
 					'size' => 2,
 					'maxlength' => 5,
-					'desc' => $this->l('Full language code (e.g. EN-US, PT-BR)')
+					'desc' => $this->l('IETF language tag (e.g. en-US, pt-BR).').' '.sprintf('<a href="http://en.wikipedia.org/wiki/IETF_language_tag" target="_blank">%s <img src="../img/admin/external_link.png" class="icon-top" /></a>', $this->l('IETF on Wikipedia'))
 				),
 				array(
 					'type' => 'text',