I have a website that because of an ill-prepared apache conf file has instructed users to cache a website URL several years into the future. As a result, when a person visit
I realize this question is very old, but I have a viable answer:
Of course you can force new URL's to avoid common caches (not long term ones)...
I.e.
However in a scenario like this (formerly edited apache .conf for long time caching) since you cannot change the domain for SEO purposes, there is a 'crude hack' you can use which will minimize the impact to SEO:
Copy your index page (i.e. index.php) to a new page (i.e. index_new.php) and edit httpd.conf (or equivalent) so that the DirectoryIndex is the new page. Then just delete or move your old page, it should theoretically always redirect to the new page.
I.e. in Debian/Ubuntu:
cd /var/www
cp index.php index_new.php
sudo vim /etc/apache2/sites-enabled/000-default
...
DirectoryIndex index_new.php
mv index.php index_old.php
sudo service apache2 restart
And there you go.