w https://developer.mozilla.org/en-US/docs/Web/CSS/calc The calc() CSS function can be used anywhere a <length>, <frequency>, <angle>, <time>, <number>, or <integer> is required. With calc(), you can perform calculation
CSS calc() allows you to mix and match units to get real-time calculations. It's useful when you need to size elements but you have some unknown number that you have to account for.
1.块级元素 A:特点: A.1默认显示在父标签的左上角 A.2块级元素默认占满一行(占满整个文档流) B:常见的块级元素 P h1--h6 ul li ol li div hr table 2.行内元素(内联元素) A:常见的=行内元素有 a span img input B:行内元素的特点 B.1 大小受到文字区域影响,不受width height 影响 B.2 行内元素不会单独占满一行 3. 行内元素和块级元素相互转换 A: 行内元素转换成块级元素