1. html syntax
Tag class: closed, non-closed, <></>, </>
property="value"
html5:<!DOCTYPE html>
html<html></html>=头<head></head>+身体<body></body>
2. html tags
segment: p
newline: br
block: div
font: font
3. html attributes
Alignment: align, left, center, right
Size: size, 1, 2, 3, ..
color: color