Topic 1: Physical v. Online
One of the best lessons I took from this chapter is that more often than not the web page layout will resemble the physical entity. I like this because it makes it easier to visualize the website as you are coding. Once you match up things like headings and subheadings with tags in HTML the code starts to make much more sense.
Topic 2: Breakdown of the Rules
CSS rules are composed of two parts, the selector and the declaration, these parts combined allow the rule to communicate with the associating HTML elements and change how they are displayed. The selector is the first part of the equation, it is a letter or word that corresponds with a tag in your HTML and tells the rule which element it is applying to. The next part is the declaration, this is the part that refers to how the element should be styled, the declaration is split into a property, that refers to that aspect you wish to change, and a value, which specifys the settings you want for the property.
Topic 3: Traversing the Cascade
There are several rules that apply to the way that the style sheet applys to the HTML, the main one being that the rules cascade down meaning that the last rule wins. There are a couple ways to get past this overarching rule, the main two being specificity and important. Specificity means that selectors that are more specific will take precedence over general ones. You can also add !important after a property which will make that rule more important than other rules for that element.