Can anybody use the api to get xml?

I have two accounts, one is A, the other is B.

Account A created a application test_a, and B grant read and write to test_a, and also return a t.
Account A use its secret and B’s t to generate a password. Using the password, I put the url(https://API_TOKEN:1ba5724e09779250cf27d19ab12bae6e@B.myshopify.com/admin/orders.xml) in my IE, at the first begniing, it works, but when I log out B, I get an error 404

I am totally crazy….

where did I do wrong?