1. Development history: HTML5 came into being in 2014. 2. CSS; HTML syntax specification: single tag: < tag name />; Double tag: < tag name attribute =” Attribute Value “></ Tag name > 4, common tags: (1) title tag: H1 ~ H6 H1 usually place important content (such as logo), characteristics: the font is smaller, bold trace is thinner and thinner (2) paragraph wrap tag form: