Check and fix html coding

Hi all, I have a basic website [login to view URL] it has Paypal buy now buttons but im having some problems. It will allow buyers to complete payment, i've just had an email from one buyer saying telling me the Error It says cookies not installed. I also find alot of orders that come through there are no detail for the order for example no call sign or design number but on the customers conformation email all the details are on that but not on my email from paypal. I'm guessing a bit of coding is missing which is beyond me. Thanks Barry