But you can override these by setting your own style descriptions. They can appear in the head section of each HTML document - but this means you need to make sure that the same style sheet is in each. Or they can be kept in a separate file, to which each HTML document refers. I use style sheets on all my sites. If I change an element in the style definition, such as making H5 headers green, not red, then all H5 headers in all documents on the site will change.
Style sheets can be tricky to manage, but they are very powerful.
For ensuring that a site has consistent design, they are hard to beat. But to make them work for you, you need already to have a sense of a hierarchy of headers and other elements. Imitation is the best form of flattery One very good way to design pages is to find sites with design that you like, save the HTML file, and then replace the original text with your own text, or some holding content, until you are ready to put in the text you need. The point here, is to retain table structures and perhaps some colour coding, while replacing entirely the text and images in the original. Finally A few simple rules can save you bother later.