HTML+CSS学习笔记（6）
认识CSS样式
CSS全称为“层叠样式表 (Cascading Style Sheets)”，它主要是用于定义HTML内容在浏览器内的显示样式，如文字大小、颜色、字体加粗等。
如下列代码：
p{ font-size:12px; color:red; font-weight:bold;}使用CSS样式的一个好处是通过定义某个样式，可以让不同网页位置的文字有着统一的字体、字号或者颜色等。
CSS样式的优势
大丈夫当如此！是英雄，分我杯羹！年少轻狂，只记得眉心一点。举手与天竞自由，豪情纵，胸怀敞。
为什么使用css样式来设置网页的外观样式呢？上面一段文字，我们想把“是英雄”、“豪情纵”、“年少轻狂”这三个短语的文本颜色设置为红色，这时就 可以通过设置样式来设置，而且只需要编写一条css样式语句。
第一步：把这三个短语用括起来。
第二步：写入下列代码：
span{ color:red;}代码如下：
<!DOCTYPE HTML><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>CSS样式的优势</title><style type="text/css">span{ color:red;}</style></head><body> <p>大丈夫当如此！<span>是英雄</span>，分我杯羹！<span>年少轻狂</span>，只记得眉心一点。举手与天竞自由，<span>豪情纵</span>，胸怀敞。</p></body></html>CSS代码语法
css 样式由选择符和声明组成，而声明又由属性和值组成，如下图所示：
选择符：又称选择器，指明网页中要应用样式规则的元素，如本例中是网页中所有的段（p）的文字将变成蓝色，而其他的元素（如ol）不会受到影响。
声明：在英文大括号“｛｝”中的的就是声明，属性和值之间用英文冒号“：”分隔。当有多条声明时，中间可以英文分号“;”分隔，如下所示：
p{font-size:12px;color:red;}注意：
1、最后一条声明可以没有分号，但是为了以后修改方便，一般也加上分号。
2、为了使用样式更加容易阅读，可以将每条代码写在一个新行内，如下所示：
p{ font-size:12px; color:red;}CSS注释代码
就像在Html的注释一样，在CSS中也有注释语句：用/*注释语句*/来标明（Html中使用)。就像下面代码：
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