Here is some text, in Arial (or another sans-serif font), that is 12 points in size, and blue
This is some regular paragraph text. Notice that it is indented, which is also possible with CSS. The standards apply here - arial, 12 point, and a nice normal black colour.
This is some more paragraph text, but with a class applied that makes it blue. Classes makes it possible to selectively apply a style to a tag without having to re-do the tag entirely.
Here is an example of an ordered list with a contextual style applied. The numbered items in it appear in green text. A regular unordered list follows, and the bullets haven't been affected.
This paragraph shows how IDs and classes can go together to alter a tag's rendering. This paragraph is standard, with black text, arial font, and an indent of 20 points.
This some bold text, because of the bold class attribute affecting it.
This last paragraph is both bold AND green, because it is affected by both a class and an ID.