Regardless, it is a bottom-up or inside-out building model for a website or application.
You first focus on the content and mark it up with semantic and meaningful HTML. This is the first layer, “structure.” After the content is properly marked up, we can move onto layer two, “presentation.” On the presentation layer, we deal with CSS. The third layer of progressive enhancement, “behavior,” we deal with last.
Putting so much emphasis on content makes sure that your content is always accessible, no matter what. When you hear the term accessibility , you probably jump right to thinking about disabled users, and you would be right to assume that, but there is more to it than that. Maybe there’s a slow connection or tight bandwidth, but 9 out of 10 times the content will still be able to render because it will be meaningful and lightweight by not being bogged down with
Keeping your HTML clean, meaningful, and semantic will ensure that your content is easily consumable by everything from a constricted bandwidth to a disabled user accessing your site through screen reading software.
Everything has meaning and nothing has design.
The first step in progressive enhancement is to lay the content out, structured in a meaningful way with HTML. Headings are marked up as headings creating a hierarchical flow, paragraphs are wrapped in <p> ’s, lists are marked up as lists, and we make sure that the HTML is meaningful without communicating anything about the design.
All content must be reachable without CSS.
Building for the Future