searchform.php

<?php $placeholder = esc_attr__('Search', 'blankout'); ?>
<form role="search" method="get" id="searchform" action="<?php echo home_url('/'); ?>" class="input-group">
	<?php if (get_search_query() == '') : ?>
		<input type="text" value="" name="s" id="s" placeholder="<?php echo $placeholder; ?>" class="form-control" />
	<?php else : ?>
		<input type="text" value="<?php the_search_query(); ?>" name="s" id="s" placeholder="<?php the_search_query(); ?>" class="form-control" />
	<?php endif; ?>

	<span class="input-group-btn">
		<button type="submit" id="searchsubmit" class="btn btn-default">Go</button>
	</span>
	<?php // no submit button version <input type="hidden" id="searchsubmit" /> ?>
</form>

<?php // alternate version
/*
<form class="form-search" action="/" method="get">
<div class="input-append">
	<input type="text" name="s" class="span7 search-query">
	<button type="submit" class="btn">Search</button>
</div>
</form>
*/
?>