Simple #JQuery to validate any column or field value in SharePoint:

<script src="/sites/rndsite/Style%20Library/jquery-1.8.1.js" type="text/javascript">  </script>
  <script type="text/javascript">
     function PreSaveAction() {
alert('hi');// just to debug script , remove while move in production
alert($("select[title='Fieldname']").val()));
           if($("select[title='Fieldname']").val() ==' ')          {
          alert('Serial number field is Empty: Please enter some value');// just to debug script, remove while move in production
          return false;
          }
            }
    </script>