title: javascript Unable to get property 'value' of undefined or null reference
body: <p>I have below code and java script is throwing error "Unable to get property 'value' of undefined or null reference". What am I doing wrong ? below is the sample code I am trying to execute to validate one input field.</p>
  
  <pre><code>&lt;html lang="en" xml:lang="en" xmlns="http://www.w3.org/1999/xhtml"&gt;
  &lt;head&gt;
      &lt;title&gt;&lt;/title&gt;
      &lt;meta content="text/html;charset=iso-8859-2" http-equiv="content-type" /&gt;
  
  &lt;script type="text/javascript"&gt;
   function validate_frm_new_user_request()
  {
      alert('test');
      valid = true;
  
      if ( document.frm_new_user_request.u_isid.value == '' )
      {
          alert ( "Please enter your valid ISID Information." );
          document.frm_new_user_request.u_isid.focus();
          valid = false;
      }
  return valid;   
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body
  &lt;form method="post" action="" name='frm_new_user_request' id="frm_new_user_request" onsubmit="return validate_frm_new_user_request();"&gt;
  &lt;center&gt;
  &lt;table&gt;
      &lt;tbody&gt;
  
          &lt;tr align="left"&gt;
              &lt;td&gt;&lt;Label&gt;ISID&lt;em&gt;*:&lt;/Label&gt;&lt;input maxlength="15" id="u_userid" name="u_userid" size="20" type="text"/&gt;&lt;/td&gt;
              &lt;td&gt;
  
  &lt;tr&gt;
              &lt;td align="center" colspan="4"&gt;
                  &lt;input type="image" src="images/button/btn_create_request.gif" border="0" ALT="Create New Request"&gt;
  
                  &lt;/td&gt;
          &lt;/tr&gt;
      &lt;/table&gt;
  &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>