Why are the changes that I made in a CSV file not saved? For example, I change the style of a cell to "Numbers". I save the file, but when I open the file again, the changes aren't saved.
CSV files contain only data, as comma-separated values. If you want to keep your formatting changes, save the file as an Excel file (i.e. myfile.xls), using the 'save as' file menu option.
Because csv only contains data, not style. If you want to save style save as
CSV files can't contain styling. Any styling you apply will only exist for that editing session.
If you want to preserve styling, save in a different format, such as XLS.
CSV files contain only data.
You can ensure Excel helps prevent formatting loss with its automatic Save As dialogue box. You can disable/re-enable the Save As box by going to File-->Options-->Save-->'Show data loss warning when editing comma delimited files'.