authorize.net Sim or Aim Difference?

[hello]

I just set up an authorize.net account and choose Sim because it's the first one. Which one should I choose? This is a basic website selling a few items and is not going to be huge.

I follow the directions I put in a 5 letter md5 keyword and updated that in the authorize.net website. In the Authorization Mode, what does Authorize and Capture means? I put in authorize for now and put in testing mode.. Right now I see that it is in Pending Mode.

For Gateway I put in Offsite..

Now when I test the order out on my website I choose Credit Card and go to proceed and got this error message?

The following errors have occurred.
(99) This transaction cannot be accepted.

What happen? and should I keep the Sim or change it to Aim. Is Aim easier? Thank you!


ps. there is no credit card logos on the credit card payment pay? Just Mycard logo...

[hello]

I got it working. I left it in sim mode for now.

[Ajeh]

AuthorizeNet AIM is the better of the two ... I would suggest you switch to AIM ...