<?php if ( !is_search() ) { $search_text = "search here"; } else { $search_text = "$s"; } ?>
<form method="get" id="searchform" action="/">
	<p><input type="text" value="<?php echo esc_attr( $search_text ); ?>" name="s" id="s" onfocus="if (this.value == 'search here') {this.value = '';}" onblur="if (this.value == '') {this.value = 'search here';}" />
	<input type="submit" id="searchsubmit" value="Go" /></p>
</form>