You can set notifications to find out when your collaborators have modified your spreadsheets, and learn what sheets or cells they've modified. You can also choose how often you'd like to be notified.
Google Docs or these days Google Drive can make collaborating with your colleagues or friends much easier by sharing Google Document, Spreadsheet, Presentation, Pictures or a whole folder.
I will show you how you find out if a website of your choice is using cookies. If the result is positive, you also find out which cookies are being used and what's their purpose.