<nav class="navbar navbar-static-top navbar-inverse" ng-controller="NavbarCtrl">
  <div class="container-fluid">
    <div class="navbar-header">
      <a class="navbar-brand" href="/">
        <span class="glyphicon glyphicon-home"></span> {{'LABEL_INTRO_HOME_TITLE' | translate:translationData}}
      </a>
    </div>

    <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-6">
      <ul class="nav navbar-nav">
        <li><a ng-href="http://dbflute.seasar.org/ja/manual/function/helper/intro/index.html">Intro's Document Page</a></li>
        <li><a ng-href="http://github.com/dbflute/dbflute-intro">Intro's Github Page</a></li>
        <li><a ng-href="http://dbflute.seasar.org/">DBFlute Top</a></li>
      </ul>

      <ul class="nav navbar-nav navbar-right">
        <a href="" ng-click="changeLanguage('en')">{{'BUTTON_LANG_EN' | translate:translationData}}</a>
        <a href="" ng-click="changeLanguage('ja')">{{'BUTTON_LANG_JA' | translate:translationData}}</a>
      </ul>
    </div>
  </div>
</nav>

<nav class="navbar navbar-static-top navbar-inverse" ng-controller="NavbarCtrl">
  <div class="container-fluid">
    <div class="navbar-header">
      <a class="navbar-brand" href="/">
        <span class="glyphicon glyphicon-home"></span> {{'LABEL_INTRO_HOME_TITLE' | translate:translationData}}
      </a>
    </div>

    <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-6">
      <ul class="nav navbar-nav">
        <li><a ng-href="http://dbflute.seasar.org/ja/manual/function/helper/intro/index.html" target="_blank">Intro's Document Page</a></li>
        <li><a ng-href="http://github.com/dbflute/dbflute-intro" target="_blank">Intro's Github Page</a></li>
        <li><a ng-href="http://dbflute.seasar.org/" target="_blank">DBFlute Top</a></li>
      </ul>

      <ul class="nav navbar-nav navbar-right">
        <a href="" ng-click="changeLanguage('en')">{{'BUTTON_LANG_EN' | translate:translationData}}</a>
        <a href="" ng-click="changeLanguage('ja')">{{'BUTTON_LANG_JA' | translate:translationData}}</a>
      </ul>
    </div>
  </div>
</nav>

Add `target="_blank" to navigation link of external resources`
Add `target="_blank" to navigation link of external resources`
