Why would I want to put information on my web page that is not visible to the typical viewer?

I would want to put information on my web page that is not visible to the typical viewer because the web page shouldn't be too simple. The information that is not visible to the typical viewer can create a visually, engaging web page. If the webpage has the information visible, it won't be very entertaining. A typical visitor doesn't need to know about doctype, metadata, and other tags.Metadata is needed even if it doesn't show up on the page. It is information necessary to web browsers using the page.