html进阶css（1）_html/css_WEB-ITnose
<br /><!doctype html><html><head> <meta http-equiv="content-type" content="text/html"; charset="utf-8"> <title>html和css的关系</title> <style type="text/css"> h1{ font-size:12px; color:#930; text-align:center; }<br /> span{<br /> color:yellow;<br /> } </style></head><body> <h1 id="span-Hello-span-World"><span>Hello</span> World</h1><br /></body></html>css的组成：选择器，声明=属性与属性值
css的语法：选择器{属性：属性值；}
说明：1）属性和属性值之间用：连接，声明必须要在花括号内
2）一个选择器可以有多个属性，属性和属性之间用；分号隔开。
3）一个属性可以用多个属性值，属性值与属性值之间用空格隔开
meta标签支持html中的全局属性。
http-equiv属性为名称/值对提供了名称。并指示服务器在发送实际的文档之前先要传送给浏览器的mime文档头部包含名称/值对。
当服务器向浏览器发送文档时，会先发送很多名称/值对。虽然有些服务器会发送许多这种名称/值对,但是所有服务器都至少要发送一格：content-type:text/html。这将告诉浏览器准备一个接受的html文档。（当然现在大多数浏览器都能自动识别HTML文档）
style type="text/css" 这段代表中间内容的风格是css格式。
例如：font-size:12px 是控制字体的大小
color:#930 是控制字体的颜色
text-align:center 是控制文字居中
span标签没有语义的它的作用就是为了设置单独的样式。在两种颜色或更多种颜色中它会选择最下面那种颜色。
<!doctype html><html><head> <meta charset="utf-8"> <title>css之中的三种语法</title> <link href="css的文件地址.css" rel="stylesheet" type="text/css" /> <style type="text/css"> span{ color:blue; font-size:20px; } </style></head><body> <p style="color:red；font-size:12px">这里的颜色是红色</p> <p>这是另外的<span>一个段落</span></p></body></html>以上是3种css的格式： 1）内联样式表就是<p style="color:red；font-size:12px"></p><br />css内联样式表就是把css代码直接写在现有的html标签中。<br /> 2)嵌入式样式表<style type="text/css"></style><br />嵌入式css样式就是可以把css样式代码写在style标签之中。一般情况下嵌入式css样式写在<head></head>之间。<br /> 3)外联样式表
<link href="css的文件地址.css" rel="stylesheet" type="text/css" /><br />外联css样式就是把css代码写在一个单独的外部文件中，这个css样式文件以".css"为扩展名，在<head>内（不是在<style>标签内）使用<link>标签将css样式文件链接到html文件内。
注意：rel="stylesheet"type="text/css"是固定写法不可修改，使用外联样式的好处可以让用户打开网页的速度有所提升。<br />三种样式表如果在同一个标签内，它们的优先级：内联>嵌入>外联。
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