font Property font CSS 属性
CSS font 属性的语法为
font: font-style font-variant font-weight font-size/line-height font-family|caption|icon|menu|message-box|small-caption|status-bar|initial|inherit;
其实就是font-style、font-variant、font-weight、font-size、line-height、font-family属性的简写，
至于caption、icon、menu、message-box、small-caption、status-bar属性不比较不常用，
而且我也不知道如何用，所以就先忽略。
在使用font简写时，其中font-size、font-family两属性是必要指定的，缺一不可。
<body>
This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph.
This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph. This is a paragraph.