function showHide(element_id) {
               
                if (document.getElementById(element_id)) { 
                   
                    var obj = document.getElementById(element_id); 
                     
                    if (obj.style.display != "block") { 
                        obj.style.display = "block"; 
                    }
                    else obj.style.display = "none"; 
                }
                
                else alert("Ýëåìåíò ñ id: " + element_id + " íå íàéäåí!"); 
            }