Changes to CSV File leaving it incompatible

Hi everybody

Actually i'm a web developer.

There is option in my website backend to update(as well as download) product related all info through CSV File.
But what problem is that when i'm doing changes to downladed file it shows error(Please see attached error.jpg file).

And that's why, when i uploads same file in my backend it's values doesn't reflect on website.

So please tell me is there any way to avoid that.

Thanks,
Rahul.