Authorize.net transaction error

When processing transactions using authorize.net, I get an error response that says:
"(TESTMODE) This account has not been given the permission(s) required for this request."

In ecart, I used the login id I use to login to the authorize.net site (not the ID that was paired with the transaction key they provide). Am i getting this error BECAUSE the account is in testmode, or is the "testmode" part of the response just simply telling me that the response came from the testmode server? The account's been active only for a couple of hours now, so I am suppose to wait like 24 hours or something before my account has permission to process credit card requests?

Also, this is probably a pretty stupid question, but at some point I thought I read that authorize.net provides a sercurity cert when you use their services. Is this true or was I just mistaken, and if it is true how exactly do you make use of it?