Demo of textarea box with minlength & maxlength
Enter 10 chars ( less than 20 chars ) in textarea and check the status. Try to increase more than 50 chars inside textarea.
HTML
<form method=post>
<TextArea name='txtArea1' rows="3" cols="70" maxlength=50 minlength=20></TextArea>
<br>
<input type="submit" value="Check"></input></form>