Every time I post a transaction to my Developer Account, it indicates that my Serial Number is wrong. Whats wrong with it?
You must be sure that you are posting the test transaction to the developer environment. Details on how to do this can be found in the Skipjack Integration Guide. You should also verify that the HTML Serial Number that you are using is the correct one for your developer account. Finally, if you are passing a Developer Serial number with each transaction to support advanced Skipjack functions, you should validate that the Skipjack account contains the correct Developer Serial Number.