[Dilettante_Pro]

<a href="#search-searchword" >Что-то нужное</a>
<input name="searchword" placeholder="Поиск" id="search-searchword" size="30" maxlength="200" value="" class="inputbox" type="text">
<script>
document.querySelector('a').onclick = function() {
   document.querySelector('#search-searchword').value = this.innerText;
}
</script>