function hideSelects()
{
    var arr_selects = document.getElementsByTagName("select");
    
    for (i=0; i<arr_selects.length; i++) {
        arr_selects[i].style.visibility = 'hidden';
    }
}

function showSelects()
{
    var arr_selects = document.getElementsByTagName("select");
    for (i=0; i<arr_selects.length; i++) {
        arr_selects[i].style.visibility = 'visible';
    }
}