validate form with javascript

I have a form in which I validate the email address using a php function then alert the operson if the email address is not correct. However, I would like to pop up an alert with javascript if the email field is left blank. I am using the function below but it down't work with php, probably works great with a cgi. Does anyone have a better way to do this? Chris Mason Code: in the head function validForm(replyForm) { if(replyForm.email.value==\"\"){ alert(\"You must enter an email address\") replyform.email.value.focus() return false } return true } in the form: <FORM onSubmit=\"return validForm(this)\" METHOD=\"POST\" ACTION=\"reserve.php3?action=send\" ENCTYPE=\"x-www-form-urlencoded\"> <table> <TR CLASS=\"$c\"> <TD CLASS=\"$c\">E-Mail </TD> <TD COLSPAN=\"$i\"><INPUT TYPE=\"text\" NAME=\"email\" VALUE=\"$email\" SIZE=\"50\"></TD></TR> </table> </form> ")