I am maintaining a website for my mother where she is displaying her paintings, www.taimiborg.se
Yesterday I made an update to a page, Utställnignar/Upcoming exhibitions. I could see the new page immediately but some 12 hours later my mother called me and said she constantly got the old page.
It seems to me that it was a cache issue because when I told her to refresh the page the new one appeared.
I usually don't have problems like this since I have set the cache in all my browsers to small sizes and frequent clearing. However, there must be many users like my mother who don't really know what a cache is and why one can refresh a page. So now I am faced with the risk that they too have old pages in their cache and will not see the new updated pages when they revisit the site.
Actually I thought that this was somewhat of a non-problem and that even if IE/Firefox/Opera has allowed cache sizes of 200mb (and thus will keep files for a long times before it automatically starts purging to make room for newer files), that once I close my browser and then restart it, when loading a page my browser will compare the cached page to the requested page. I thought this was normal cache behaviour of browsers, but the experience of my mother suggests otherwise.
So I wonder: when developing websites, what is the standard method for trying to ensure that a visitor is viewing the most up-to-date pages rather than some old cached ones on their harddrives? Should cookies be used for this? Or some meta-tag?
Please bear in mind that I am not a professional HTML programmer (obviously) so I appreciate pedagogical answers.