<script> function validateForm() {   var x = document.forms["myForm"]["fname"].value;   if (x == "") {     alert("Name must be filled out");     return false;   } } </script> <form name="myForm" action="/action_page.php" onsubmit="return validateForm()" method="post" required>   Name: <input type="text" name="fname">   <input type="submit" value="Submit"> </form>   

   <script>   function validateForm() {     var x = document.forms["myForm"]["fname"].value;     var errorSpan = document.getElementById("error-message");      if (x == "") {       errorSpan.innerHTML = "Name must be filled out";       return false;     } else {       errorSpan.innerHTML = ""; // Очищаем сообщение об ошибке, если поле заполнено       return true;     }   } </script>  <form name="myForm" action="/action_page.php" onsubmit="return validateForm()" method="post" required>   Name: <input type="text" name="fname">   <span id="error-message" style="color: red;"></span> <!-- Элемент для отображения сообщения об ошибке -->   <br>   <input type="submit" value="Submit"> </form>