1. The declaration tag of css tells the browser what form it should use to parse you, usually: Because html5 supports downward compatibility, see the details Pictured above.

2. How to use css style:
(1) Internal link style sheet:
demo.html

  
  
  
      
      
  
  
    
内链样式使用
  
    
  
    内链样式使用  
    
  
  

(2) Embedded style sheet:
demo .html

  
  
  
      
      
      
  
      
  
    
嵌入式样式
  
    
嵌入式样式
  
  
  

(2) Introduced style sheet:
demo.htnl

  
  
  
      
      
      
         
      
      
     
  
  
    
引入式样式
  
    百度  
    
  
    
引入式样式
  
    
css的html选择器
  
  
  

style.css

/* HTML样式定义   */  
body{  
    background-color:yellow;  
    color:#fff  
}  
  
div{  
    background:red;font-size:20px  
}

The above is the css folding style (1 ) - Contents on three ways to use css styles. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!