Your web page design should be accessible to people with impairments and disabilities. The size of the text should be able to be adjusted by the user– this helps people with visual impairments. The web site should also be accessible when viewed in a plain text browser.
Another thing that needs to be taken into account is the resolution of your visitor’s screen (monitor). The web page design should still be useable on small screen resolutions.
Your web site needs to be run on a web server that is professionally maintained. A server will only be secure if it is managed by someone who knows what they are doing. The server needs to be located in secure premises with strong physical security.
Credit card numbers need to be encrypted before being sent over the Internet, and they should never be emailed! If credit card numbers need to be stored, they should be encrypted and stored for the shortest time possible.
Ideally, your web site should be hosted on a ‘cluster’ of servers so that if any one server fails, the others can take over without interruption to your website. All web site data should be backed-up on a regular basis.