function ismail(em) {
  var str = em; // 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
  return false;
}

function iszip(zip) {
var str = zip;
if((str.length < 5) || isNaN(str)) {
  return false;
  }
 return true;
}



function validfrm(frm) {
 
var email1= frm.email1.value;
var email2= frm.email2.value;
var first = frm.firstname.value;
var last = frm.lastname.value;
var zip = frm.zip.value;

//alert("email: "+email1);
//alert("email2: "+email2);
//alert("first: "+first);
//alert("last: "+last);
//alert("zip: " + zip);

if ( email1 == "" || email2 == "" || first == "" || last == "" || zip == "" ) {
alert ("all items must be filled out");
 return false;
}

if ( email1 != email2 ) {
alert ("emails don't match");
 return false;
}

if ( ismail(email1) == false ) {
alert("email invalid; mail must be for myaddr@mymailco.com");
 return false;
}

if (iszip(zip) == false ) {
 alert("zip code must be 5 digits");
 return false;
}

 return true;
}