Cookies
Internet Explorer: https://support.microsoft.com/en-us/help/17442/windows-internet-explorer-delete-manage-cookies
Mozilla Firefox: https://support.mozilla.org/en-US/kb/cookies-information-websites-store-on-your-computer?redirectlocale=en-US&redirectslug=Cookies#w_cookie-settings
Google Chrome: http://www.google.com/support/chrome/bin/answer.py?hl=en&answer=95647
Safari: https://support.apple.com/cs-cz/HT201265
Opera: http://www.opera.com/help/tutorials/security/cookies/