[codedokode]

If the content is dynamic (e.g. a list of popular articles in a sidebar has changed), then the page will be considered "updated".

[wise_young_man]

This is not correct. It’s up to the server, controlled by the application to send that or other headers. Similar to sending a <title> tag. The headers take priority and similar to what another person said they will do a HEAD request first and not bother with a GET request for the content.