Users will occasionally come to a page that doesn't exist on your site, either by following a broken link or typing in the wrong URL. Having a custom 404 page30 that kindly guides users back to a working page on your site can greatly improve a user's experience. Your 404 page should probably have a link back to your root page and could also provide links to popular or related content on your site. You can use Google Search Console to find the sources of URLs causing "not found" errors31.
Do not be fooled by those traffic sellers promising thousands of hits an hour. What they really do is load up your URL in a program, along with a list of proxies. Then they run the program for a few hours. It looks like someone is on your site because your logs show visitors from thousands of different IPs. What happens in reality is your website is just pinged by the proxy, no one really sees your site. It is a waste of money.