I am not suggesting that Excel is bad but I received a list of account numbers and passwords for use in a performance test. These account numbers are used as the username. The file came as a .CSV so I opened in Excel manipulated the file a bit (removed the header etc) and saved the file ready for the performance test.
During the test there where lots of login errors. After some investigation many where found not able to login, going back to the admin that provided we discovered that Excel had removed the leading zero once it had been imported into Excel. e.g 01234567 became 1234567 which didn’t exist and hence failed to login.
A bit of a duh moment and probably a humbling last post for 2013.