Separate from the text and graphics you (and your visitors) can see, your website contains a great deal of 'invisible' code required by the browser or search engine.
These updates need to be carried out by your website designer as it involves changing the code that controls how a web browser displays your pages. It may also involve changing the code required to run applications on your website, such as calendars, contact forms and slideshows, and integrating information stored in an external database.
With the advent of smartphones, there was a flurry of industry-wide updates to ensure that these visitors could view websites on a small screen. Being 'mobile-friendly' is now a website standard that companies ignore at their peril.
You should expect your website code to require updating periodically, even if your text and graphic content remains the same.