To know if a website is using cookies to track your online activities, you should do the following:

1. Check the website’s privacy policy. Most websites post their policies and describe what type of information is collected and how that information is used.
2. Read the Dialog box that displays when you first visit a website. Most websites alert users to the use of cookies.
3. Check the browser settings. You can typically find options for controlling cookies in the preferences or security settings.
4. Check the browser. Some browsers will provide notices when cookies are received or provide additional features for rejecting cookies.