<SCRIPT LANGUAGE="JavaScript">
<!--

function valid(form) {
  var field = form.email; // email field
  var str = field.value; // email string
  var reg1 = /(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/; // not valid
  var reg2 = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/; // valid
  if (!reg1.test(str) && reg2.test(str)) { // if syntax is valid
    alert("Thank your for your feedback."); // this is optional
    return true;
  }
  alert("\"" + str + "\" is an invalid e-mail!"); // this is also optional
  field.focus();
  field.select();
  return false;
}

// -->
</SCRIPT>
<FORM METHOD="POST"
      ACTION="mailto:you@yourdomain.com"
      ENCTYPE="text/plain"
      onSubmit="return valid(this)">
Your e-mail address:<BR><INPUT TYPE="text" NAME="email" SIZE="40"><BR>
Subject:<BR><INPUT TYPE="text" NAME="subject" SIZE="40"><BR>
Comments:<BR><TEXTAREA NAME="comments" COLS="40" ROWS="5"></TEXTAREA><BR>
<INPUT TYPE="submit" VALUE="Send Mail">
</FORM>