IE Changes .csv to .xls

When clicking on an anchor link that points directly at a .csv file, IE prompts the user to save or open the file as an Excel spreadsheet. If the user saves it, its saved with a .xls extension. The same thing happens if the user right clicks on the file. It shows up in the save dialog with a .xls extension.

When excel opens a .csv file renamed to .xls, each row of
data is scrunched together into a single cell with quotes
commas and all.

How to fix:

Add MIME type .csv to IIS web server properties.