<form class="searchform" action="/" id="bigsearchform" method="get" role="search">
    <input class="searchfield" type="text" id="s" name="s" value="Поиск..." onfocus="if (this.value == 'Поиск...') {this.value = '';}" onblur="if (this.value == '') {this.value = 'Поиск...';}" /><?php wp_dropdown_categories( 'show_option_all=Везде' ); ?>

<input class="searchbutton" type="submit" value="Go" />

    </form>