View file protected/views/index/error.php

<div class="title"><b>{{ Lang.get('error') }}</b></div>
<div class="post">
<div style="float:left; padding: 2px;">{{ System.image('error.png')|raw }}</div> <span style="padding: 2px;">{{ Lang.get('error_text')|raw }}</span>
</div>
<div class="block">
{{ System.image('back.png')|raw }} <a href="/">{{ Lang.get('mainpage') }}</a>
</div>