how to remove blank page at checkout
 

When a user selcects submit at the final checkout step, their is a blank page that appears saying your order is being processed, and then you are redirected to the invoice page.

How can I just have it direct to the print invoice page and not have the blank white page displaying your order is being processed show?

You'll find that most carts have a 'order being processed page'. You can edit that page if you want to make it look nicer, but it only displays briefly as the payment gateway is approving the order.