function open_menu(num){

        if(num=='next' && opened<4) num=1+opened;
        else if(num=='prev' && opened>1) num=opened-1;
        else if(num<1 || num>4 || num=='next' || num=='prev') return false;

        if(opened>0){
            $('#menu'+opened).removeClass();
            $('#dsc'+opened).hide();
        }

        $('#menu'+num).addClass('active');
        document.getElementById('srcimg').src='../sys/images/l_hiw_d_img_'+num+'.jpg';
        $("#dsc"+num).animate({opacity: "show"}, "slow");

        opened=num;

    }