function dajenter(e){
 if (tip=='Gecko') { 
    var kod=e.which
    } 
 else{
    var kod=e.keyCode
    }
 if(kod==13) {
    proveriLogin()
    }
}

function proveriLogin(){
  if (document.login.username.value == ''){
     window.alert('Please enter username!');
     document.login.username.focus();
     return;
  }
  if (document.login.password.value == ''){
     window.alert ('Please enter password!');
     document.login.password.focus();
     return;
  }  
document.login.submit();
}