<div class="radikalwp-fm-error"><input type="password" value="123456" /><span>رمز عبور حداقل ۸ کاراکتر باشد<//span><//div>

.radikalwp-fm-error { width: 250px; }
.radikalwp-fm-error input {
  width: 100%;
  padding: 12px 14px;
  font-family: inherit;
  font-size: 14px;
  color: #0f172a;
  border: 1.5px solid #ef4444;
  border-radius: 12px;
  outline: none;
  box-sizing: border-box;
  animation: radikalwp-fm-shake .4s ease;
}
.radikalwp-fm-error input:focus { box-shadow: 0 0 0 3px rgba(239, 68, 68, .15); }
.radikalwp-fm-error span { display: block; margin-top: 6px; font-size: 11px; color: #ef4444; }
@keyframes radikalwp-fm-shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-5px); }
  50% { transform: translateX(5px); }
  75% { transform: translateX(-3px); }
}