2. 如何让<h3>始终为黑色，而<em>在不被<h3>包含的情况为红色：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<meta http-equiv="Content-Language" content="gb2312" />
<title>test</title>
<meta name="Author" content="doyoe(飘零雾雨), edzmaster@gmail.com" />
<style type="text/css">
h3,h3 em {
color:#000;
}
em {
color:#f00;
}
</style>
</head>
<body>
<h3>讨论<em>CSS</em>优先级</h3>
<p>讨论<em>CSS</em>优先级</p>
</body>
</html>
固定效果：
固定代码：
<h3>讨论<em>CSS</em>优先级</h3>
<p>讨论<em>CSS</em>优先级</p>
3. 如何写一个外部样式使得
<h3 style="color:#000;"> 覆盖我</h3>
的颜色为红色：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<meta http-equiv="Content-Language" content="gb2312" />
<title>test</title>
<meta name="Author" content="doyoe(飘零雾雨), edzmaster@gmail.com" />
<style type="text/css">
h3 {
color:#f00!important;
}
</style>
</head>
<body>
<h3 style="color:#000;">覆盖我</h3>
</body>
</html>
4. 如何让同时具有.a,.b样式的元素只表现.a的颜色样式：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<meta http-equiv="Content-Language" content="gb2312" />
<title>test</title>
<meta name="Author" content="doyoe(飘零雾雨), edzmaster@gmail.com" />
<style type="text/css">
.b {
color:#000;
}
.a {
color:#f00;
}
</style>
</head>
<body>
<p class="a b">传说中滴测试</p>
</body>
</html>
固定代码：
<p class="a b">传说中滴测试</p>