The title question is unfortunately pretty vague (or at least may be asking differently than what I intend)... but let me elaborate.
I know basic HTML5 and CSS. I don't need to learn the tags and how they work. What I'm looking for is some information on what sort of process to follow when actually coding a professional style website. I want to make a portfolio website for myself from scratch (that is, not to use turnkey software such as Wordpress and such) but I don't know what to do as a process to making a clean site from the start. I'm a CS student and my skill set is in Java/C#, but I do want to learn web development as well.
Do I need to have an idea of what the site is ultimately going to look like before I start the HTML? Can I just write the HTML to describe the content and worry about the look of the site afterward, or do I have to write the HTML knowing what I want the site to look like as I write it?
If I want a horizontal nav bar at the top, do the links have to be side by side in the HTML code?
These are all things I don't know... how to actually build a proper website. I know how to make basic pages with text and links and headers and all that, but to make a professional website is foreign to me. Every page I find on Google is either too high level (giving a design and implementation process without giving examples of how to implement once you know what you want) or is too beginner (trying to teach me HTML and CSS when I already know what I need to know in that regard).