function getEl(id){
 if(document.getElementById != null){
  return document.getElementById(id);
 }
 if(document.all != null){
  return document.all[id];
 }
 if(document.layers != null){
  return document.layers[id];
 }
 return null;
}

function checkform(){
 if(getEl('name').value==''){alert('Please enter your name.'); return false;}
 if(getEl('address').value==''){alert('Please enter your address.'); return false;}
 if(getEl('city').value==''){alert('Please enter your city.'); return false;} 
 if(getEl('zip').value==''){alert('Please enter your zip.'); return false;} 
 if(getEl('phone').value==''){alert('Please enter your phone number.'); return false;} 
 if(getEl('email').value==''){alert('Please enter your email.'); return false;}  
 if(getEl('pay_online').value==''){alert('Please choose to pay online or not.'); return false;} 
 if(getEl('membership_type').value==''){alert('Please choose a membership type.'); return false;} 
 return true;
}