function isEmpty(elem){
  return trim(elem.value).length==0;
}

function validateForm(){
  if(isEmpty(f.firstname)){
    alert("Please enter first name");
    f.firstname.focus();
    return false;
  }
  if(isEmpty(f.lastname)){
    alert("Please enter last name");
    f.lastname.focus();
    return false;
  }
  if(!isEmpty(f.email) && !validateEmail(f.email)){
    alert("Please enter valid email address");
    f.email.focus();
    return false;
  }
  if(f.email.value!=f.confirmemail.value){
    alert("Email addresses do not match");
    f.confirmemail.focus();
    return false;
  }
  if(isEmpty(f.password)){
    alert("Please enter password");
    f.password.focus();
    return false;
  }
  if(isEmpty(f.confirmpassword)){
    alert("Please confirm password");
    f.confirmpassword.focus();
    return false;
  }
  if(f.password.value!=f.confirmpassword.value){
    alert("Passwords do not match");
    f.confirmpassword.focus();
    return false;
  }
  if(isEmpty(f.login)){
    alert("Please enter online name");
    f.login.focus();
    return false;
  }
  if(f.referredby.value==''){
    alert("Please select referred by");
    f.referredby.focus();
    return false;
  }
  if(f.femail1.value!='' && !validateEmail(f.femail1)){
    alert("Please enter valid email address");
    f.femail1.focus();
    return false;
  }
  if(f.femail2.value!='' && !validateEmail(f.femail2)){
    alert("Please enter valid email address");
    f.femail2.focus();
    return false;
  }
  if(f.femail3.value!='' && !validateEmail(f.femail3)){
    alert("Please enter valid email address");
    f.femail3.focus();
    return false;
  }

  f.submit();
}