[BdSBB]

Code:

function validate(f) {

   if (f.email.value != f.re_email.value) {
      alert('Your emails do not match!');
      return false;
   }
}

<form onsubmit="javascript:validate_email(this);">
<input name="email">
<input name="re_email">
... etc. ...
</form>

like this?