I'm trying to do the data import wizard exercise (https://developer.salesforce.com/trailhead/force_com_admin_beginner/data_management/data_import) and I'm getting the above error when I choose the file Trailhead tells me to download. I went searching in the forums for an answer to this and tried the one suggestion -- copying to a notepad app and re-importing into excel. It didn't work. The other "suggestion" is to change browsers. I don't find this an acceptable alternative. In addition to the time and hassle it will take to shut everything down and fire it all back up in another browser, I don't have appropriate security set up on IE and I don't trust Chrome at all. I also can't ask my users to do that every time they want to import. I've already been using the DataLoader and, where possible, DemandTools to import data. I thought this would be a chance to learn how the Import Wizard works. But all this exercise tells me is what other folks have told me before -- the Import Wizard is a pain and they don't use it. I don't expect the Trailhead forum to fix this, but I am about to load the required data using DataLoader. I hope the Challenge doesn't care how I loaded it. I will report back. But in the meantime if anyone has any useful suggestions, please chime in. Thanks.
I am not sure why the CSV file has to be MIME type. It looks like there no other way to complete that challenge as even switching to Chrome didn't work for me. I used Data Loader to complete the challenge.
