Here you will find detailed examples showing you how to set up a shopping cart. Make sure you check the FAQs too, your question has probably been answered before.
Using a hyperlink
Using an HTML form
Field names
Adding multiple items to your cart
Using a hyperlink
Using an HTML form
HTML Customer receipts
Language and currency
Sales tax
Customer messages
mTracker affiliate program
Shipping
Accepting card payments
Configure the Custom gateway
Using PayPal
Gift certificates
Discount coupons
Coupons API
Selling downloads
Scripting dynamic website
Remote call back to your website
Link verfiication
Orders API