modify username hint

configure_thurvserver.tpl

@@ -281,7 +281,7 @@ var _localLang = {
                                         <label for="customfield{$customfields[0].id}">{$customfields[0].name}</label>
                                         {$customfields[0].input}
                                         {if $customfields[0].description}
-                                            <span class="field-help-text">
+                                            <span class="alert alert-info">
                                                 {$customfields[0].description}
                                             </span>
                                         {/if}