If you looked at how the HTML we just looked at appears in a browser, you might wonder about the layout and coloring. That is all created by Cascading StyleSheets (CSS). It was actually refered to in the head section of the HTML document.
What CSS does is define how all those different tags display in the window. There are a lot of different CSS attributes that control fonts, colors, background images, underlines, margins etc. Here is a brief look at what CSS looks like and what it does.
Don't worry too much about what it all means. Just remember the format. The tag name beings the CSS style, followed by curly brackets which enclose all the information about the tag. Here is what the above code looks like in a browser.