Most of Joomla templates allows to present frontend messages to the users. One of such cases can be using <jdoc:include type="message" /> in template file, which shows
messages like "your password or username is incorrect" or " Account created". These could show on any page in the site but if that page has been viewed and caches, the user will not get the message. As its not as module position it cannot be excluded from being cached with the jot chase tags. With new JotCache plugin ver.1.2.2 is exclusion of frontend messages from page caching automatic performed.