Most web browsers have a feature that will automatically fill in your home address, phone number, email address -- and even credit card number -- when the browser detects that you're typing personal information into a form. This means your information is stored on your computer. When it comes to securing this information, you have to take charge and set your privacy preferences in the browser.

For example, Mozilla Firefox browser allows you to create a master password that you have to input before your browser can remember (and auto-fill) your username and password for a web site. Also, under Preferences > Privacy, you can select "Always clear my private data when I close Firefox." In this case, when you quit the browser software, any private information you entered while using it will be erased.

With an Internet Explorer browser, you can adjust your privacy settings under Tools > Internet Options > Content > AutoComplete > AutoComplete Settings. To automatically fill in your information, check the box that says “User names and passwords.” If you only want your browser to fill in information when you choose to, check the box that says “Prompt me to save passwords.” This way, Explorer will notify you when it is going to auto-save any of your passwords. To automatically clear your information or passwords, select either “Clear Forms” or “Clear Passwords” from the AutoComplete Settings window.