HTTP:// should be added to the Landing Page URL entry if user omits it.

HTTP:// is required. This prefix should be displayed and included in the Landing Page URL field on the Orders Info screen if the user omits entering it.

to be clear:

field is blank
user enters "www.blah.com
user moves focus to another field or SAVE
"http://" is pre-pended to the URL

but if the user only wants to save the quote without a merchant URL, then the user should be able to save without being blocked.