<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'
src='http://code.jquery.com/jquery-1.7.1.js'></script>
<script type='text/javascript'>
$(window).load(function(){
$('a').click(function(){
$('#text_tag_input').val($(this).html());
});
});
</script>
</head>
<body>
<input id="text_tag_input" type="text" name="tags" />
<div class="tags_select">
<a href="#">tag1</a> <a href="#">tag2</a> <a href="#">tag3</a>
</div>
</body>
</html>