Too many people pay developers to develop their website just to forget about it once the website is up and running. They might correct or modify some of the content over time, but that’s it.
A website is like a car and it needs maintenance – not only the content, but the core of the website. Would you really buy a car and use it every day without getting it to the mechanic at least twice a year for an oil change or an engine tune-up? Your website is kind of like a car: it won’t need its oil changed, but the code will need to be updated to keep up with the latest software updates like IIS, Apache, PHP and ASP.
True story: I once had a client whose clustered server failed due to a hardware problem. The operating system was a Linux-based version that was end of life 5 years ago. On top of that, the website hosted on this server needs to be served by Apache 1.3, which was end of life 2 years ago.
It’s now a real pain for that client’s developers to get this website up and running with the currently-supported version of Apache and PHP.
Unless you have a CMS and you frequently update it with the update management that came with it, please call your website developers once in a while and ask them to take a look at the code to make sure it’s still up-to-date.