function change_cat() {

        document.getElementById('blank').style.display='none';
        document.getElementById('blank').style.visibility='hidden';
        document.getElementById('katalog_kat_byt').style.display='none';
        document.getElementById('katalog_kat_byt').style.visibility='hidden';
        document.getElementById('katalog_kat_dum').style.display='none';
        document.getElementById('katalog_kat_dum').style.visibility='hidden';
        document.getElementById('katalog_kat_nebytove').style.display='none';
        document.getElementById('katalog_kat_nebytove').style.visibility='hidden';
        document.getElementById('katalog_kat_pozemek').style.display='none';
        document.getElementById('katalog_kat_pozemek').style.visibility='hidden';
        document.getElementById('katalog_kat_chata').style.display='none';
        document.getElementById('katalog_kat_chata').style.visibility='hidden';
        document.getElementById('katalog_kat_komerce').style.display='none';
        document.getElementById('katalog_kat_komerce').style.visibility='hidden';
        document.getElementById('katalog_kat_bytovka').style.display='none';
        document.getElementById('katalog_kat_bytovka').style.visibility='hidden';

        if (document.getElementById('nemovitost').value == 0) {
            document.getElementById('blank').style.display='block';
            document.getElementById('blank').style.visibility='visible';
        }
        
        if (document.getElementById('nemovitost').value == 1) {
            document.getElementById('katalog_kat_byt').style.display='block';
            document.getElementById('katalog_kat_byt').style.visibility='visible';
        }
        
        if (document.getElementById('nemovitost').value == 2) {
            document.getElementById('katalog_kat_dum').style.display='block';
            document.getElementById('katalog_kat_dum').style.visibility='visible';
        }
        
        if (document.getElementById('nemovitost').value == 3) {
            document.getElementById('katalog_kat_nebytove').style.display='block';
            document.getElementById('katalog_kat_nebytove').style.visibility='visible';
        }
        
        if (document.getElementById('nemovitost').value == 4) {
            document.getElementById('katalog_kat_pozemek').style.display='block';
            document.getElementById('katalog_kat_pozemek').style.visibility='visible';
        }
        
        if (document.getElementById('nemovitost').value == 5) {
            document.getElementById('katalog_kat_chata').style.display='block';
            document.getElementById('katalog_kat_chata').style.visibility='visible';
        }

        if (document.getElementById('nemovitost').value == 6) {
            document.getElementById('katalog_kat_komerce').style.display='block';
            document.getElementById('katalog_kat_komerce').style.visibility='visible';
        }

        if (document.getElementById('nemovitost').value == 7) {
            document.getElementById('katalog_kat_bytovka').style.display='block';
            document.getElementById('katalog_kat_bytovka').style.visibility='visible';
        }
    }
    
    function showimage(id) {
        window.open("show/?id=" + id ,"show_img", "directories = 0, width = 370, height = 340, location = 0, menubar = 0, resizable = 0, scrollbars = 0, status = 0, top = 100, left = 250, toolbar = 0");
    }
    
    function printitem(id) {
        window.open("print/?id=" + id ,"print_item", "directories = 0, menubar = 0, resizable = 1, scrollbars = 1, status = 0, top = 10, left = 10, toolbar = 1");
    }