See CSS Zen Garden for dramatic examples of the same HTML with vastly different CSS
Web "Sites" Part 1
HTML
Basic formatting elements
CSS
Separating content from style
Browser tools
View source
Chrome Inspector, Firebug
clear cache
view cookies, etc
Exercise: Write a web page from scratch
<!doctype html><htmllang="en"><head><metacharset="utf-8"><title>Hey, this is my awesome HTML5 document!</title><!--[if IE]>
<script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
<![endif]--></head><bodyid="home"><h1>Hello, Web!</h1></body></html>
<!doctype html><htmllang="en"><head><metacharset="utf-8"><title>HTML5 boilerplate—all you really need…</title><styletype="text/css">p {
font-color: red;
font-size: 3em;
}
</style><!--[if IE]>
<script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>
<![endif]--></head><bodyid="home"><h1>HTML5 boilerplate</h1><p>This is a big red paragraph</p></body></html>