Adding placeholder in search-field

<form method="post" action="{{ url_for('index') }}" id="search_form">

  <div id="search_wrapper">

    <input type="text" id="q" class="q" name="q" tabindex="1" autocomplete="off" {% if q %}value="{{ q }}"{% endif %}/>

    <input type="text" placeholder="{{ _('Search for...') }}" id="q" class="q" name="q" tabindex="1" autocomplete="off" {% if q %}value="{{ q }}"{% endif %}/>

    <input type="submit" value="search" id="search_submit" />

  </div>

  {% include 'categories.html' %}