function showtab(id){
    names = new Array ("tabname_1","tabname_2","tabname_3","tabname_4"); //массив id заголовков табов
    conts= new Array ("tabcontent_1","tabcontent_2","tabcontent_3" ,"tabcontent_4"); //массив id табов
    for(i=0;i<names.length;i++) {
        document.getElementById(names[i]).className = 'nonactive';
    }
    for(i=0;i<conts.length;i++) {
        document.getElementById(conts[i]).className = 'hide';
    }
    document.getElementById('tabname_' + id).className = 'active';
    document.getElementById('tabcontent_' + id).className = 'show';
}