Advanced Search Form for WordPress

I have a Advanced Search Form for WordPress

<?php
if ( function_exists( 'ot_get_option' ) ) {
    $adv_search_page_url = ot_get_option('adv_search_page_url');
}
    ?>
    <form id="advance-search" method="get" action="<?php echo esc_url($adv_search_page_url); ?>">

        <?php
        /*-----------------------------------------------------------------------------------*/
        /*  Generate Advance Search Select Box
        /*-----------------------------------------------------------------------------------*/
        function buildSelect($tax)
        {
            $terms = get_terms($tax);
            $any = __("Alle", "beerglas");
            $x = '<fieldset class="search-field"><label>' . __( str_replace("_", ucwords($tax)) , "FoodRecipe") . '</label><select name="' . $tax . '">';
            $x .= '<option value="">' . $any . '</option>';
            foreach ($terms as $term) {
                $x .= '<option  value="' . $term->slug . '">' . $term->name . '</option>';
            }
            $x .= '</select></fieldset>';
            return $x;
        }

        $taxonomies = get_object_taxonomies('beer');
        $skipTag = array_shift($taxonomies);

        foreach ($taxonomies as $tax) {
            echo buildSelect($tax);
        }
        ?>
        <fieldset>
            <input class="readmore" type="submit" value="Search"/>
        </fieldset>
    </form>

this works good only if i use my mobile (touch) phone i want to give some value’s the dropdown opens and closes inmediately and the keyboard is comming up.. annyone anny idea how to solve this?

greetz Edwin