Is it better to add the css code inside your Html file or is it better to create a css file separately and make a reference to it in your Html file.
It depends on what you're going for. For cleaner, more concise code, referencing is the way to go. Otherwise, it doesn't make too much of a difference which route you pick.
It is okay if you put in the same code file or use a link in the html file but they need to be in the same folder