CSS基础

CSS指层叠样式表（Cascading Style Sheets）

样式声明：#

选择器和优先级：#

<!DOCTYPE html>
<html>
<head>
    <script  src="js/jquery.min.js" type="text/javascript"></script>
    <title>Document</title>
    <style type="text/css">
        /*选择器的优先级： 属性选择器 > id选择器 > 类选择器 > 标签选择器*/
 
        /*标签选择器*/
        img{
            border: 10px solid red;
            width: 200px;
        }
        /*类选择器*/
        .demo{
            width: 500px;
        }
        /*id选择器*/
        #test{
            height: 200px;
            width: 300px;
        }
        /*属性选择器*/
        img[alt]  {
            padding: 20px;
            color: red;
            margin: 100px;
            border: 30px solid;
        } 
    </style>
</head>
<body>
<img src="images/girl.jpg" class="demo" id="test" alt="图片加载不成功">
</body>
</html>