var dom = (document.getElementById)? true : false;
var ie4 = (document.all && !dom)? true : false;

function user_must_fill(mess,c){
    if (mess!=''){
        var fields = 'Field';if(c>1)fields=fields+'s';
        alert(fields+' '+mess+' must be completed!');
    }
}

function show_hide(what,mode){
 if(dom)document.getElementById(what).style.display=mode;
 else if(ie4)document.all[what].style.display=mode;
}