A website today needs to react to the type of device and version of browser being used to view it. Desktops, laptops, phones. To a website, these are all very different, each with their own set of quirks. Your site needs to adapt, adjust, expand, contract as space and capabilities allow. This is called Adaptive Web Design, or AWD. I've been creating and maintaining websites for over 20 years using HTML, CSS, and JavaScript. I'm proficient using PHP which allows your site to connect to backend databases and other programs. This can be used to allow only verified users to see some of your content, to create contact pages that will send you an email or text message when a visitor clicks submit, to create programs that run on a regular schedule to notify you of any upcoming tasks. The possibilities are endless.