方法：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>首字下沉</title>
<style>
p {
width: 400px;
margin: 0 auto;
}
p::first-line {
text-transform: uppercase;
}
P::first-letter {
font-size: 4em;
border: 1px solid yellow;
background: greenyellow;
float: left;
padding: 2px;
margin-right: 5px;
}
</style>
</head>
<body>
<p>I am happy to join with you today in what will go down in history as the greatest demonstration for freedom in the history of our nation.</p>
<p>Five score years ago, a great American, in whose symbolic shadow we stand today, signed the Emancipation Proclamation. This momentous decree came as a great beacon light of hope to millions of Negro slaves who had been seared in the flames of withering injustice. It came as a joyous daybreak to end the long night of their captivity.</p>
</body>
</html>
效果：
