Once a website has been created, it's necessary to keep the content correct and up-to-date, as well as ensure the site remains secure.
The content of a website is the responsibility of the owner. Typically the technical solution of a site is such that curating the content does not requires specialized computer- or internet-related knowledge. When creating a webside, I always provide the site owner with instruction on how to keep the site in order and how to curate the content and from there on the site owner can manage it without assistance. But it must be considered that owning a website does require constant care and monitoring, to ensure the content of the page remains correct. A website is never truly complete, since there is always a perpetual need to add, change or remove content. When creating a website, it must always be considered how much sustained interest there is to continuously update the existing content. If it is forseeable that there time or resources won't be available to frequently update the content, then it's better to have less content than to have a large amount of outdated content.
Modern websites are dynamic and responsive to different screen sizes, from small smartphones to large monitors. This responsiveness and scalability makes modern websites relatively complex as a programmed environment. Even simple and consise content may have a relatively complex technological solution behind it. Unfortunately, this technical complexity also creates the inevitable risk of error in the technical code. Since the internet has no shortage of malicious actors, such errors and security holes are often exploited sooner rather than later, in order to spread malicious code and viruses, or to carry out other illegal activity. Therefore, it is necessary to always ensure the security of the site. Securing a website is often made easy by good hosting services, but the ultimate responsibility of a site's security always rests with the site's owner. Should the site owner lack the appropriate skills and knowledge, it is helpful to have a partner that takes care of security.
Creating websites, I typically use the open source engine Joomla!. Open source engines have both risks and benefits. In every case, the programming logic of the open soure engine is always available to malicious actors. However, since the community using the open source engine is large and the group of developers examining the code is wide, security flaws are found and patched relatively quickly compared to commercial engines. Thus to keep the site secure it's important to monitor that all the latest updates and security patches of the engine are installed with minimal delay as they are released. The owner of the site must keep an eye on so-called "security lists", which list patches to discovered issues as well as warnings if some tools or utilities are considered insecure at any given moment. THe security-related news of the Joomla! engine can be found here: https://developer.joomla.org/security-centre.html