Uncaught TypeError: Cannot read property 'reset' of null in Javascript

Add id to your form:

<form id="form1" role="form" name="form1" action="reg_employer.php" method="post">

or

Try:

function ValidateEmail(inputText)
{
  var mailformat = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/;
  if(inputText.value.match(mailformat))
{
  document.form1.coemail.focus();
  return true;

}
else
{
  alert("You have entered an invalid email address!Enter again");
  document.form1.reset();   //<== change this line, use form name
  return false;
}
}

Apparently I didn't have a form id in

<form id="form1" role="form" name="form1" action="reg_employer.php" method="post">

Addition of a form id resolved the issue.