I have visited a number of web site and seen that many changes made are not immediately visible in other parts of the website even if the change is critical. To avoid such stupid blunders found in best of websites, I propose a new web development tool called propagation diagram.
For every update operation in the website draw where it will effect the other parts of the website and decide if the change is critical, non critical or so. If critical the change should be made immediately and the web server cache should be also updated immediately. If non critical the change should be made in the database itself.
So are you adopting propagation diagrams today.