line-height

значения свойства:

css/style.css

.a {
 line-height: normal;
}

index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<link href="css/style.css" rel="stylesheet" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
</head>
<body>
<p class="a">Hello World!<br />To be or not to be?</p>
<hr />
<p id="p1">Hello World!<br />To be or not to be?</p>
<hr />
<p id="p2">Hello World!<br />To be or not to be?</p>
<hr />
<p id="p3">Hello World!<br />To be or not to be?</p>
<script>
/*JavaScript*/
document.getElementById("p1").style.lineHeight = "3";
/*jQuery*/
$(document).ready(function () {
$("#p2").css({ "line-height": "10px" });
$("#p3").css({ "line-height": "150%" });
});
</script>
</body>
</html>

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>New Page</title>
<link href="css/style.css" rel="stylesheet" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
</head>
<body>
<p class="a">Hello World!<br />To be or not to be?</p>
<hr />
<p id="p1">Hello World!<br />To be or not to be?</p>
<hr />
<p id="p2">Hello World!<br />To be or not to be?</p>
<hr />
<p id="p3">Hello World!<br />To be or not to be?</p>
<script>
/*JavaScript*/
document.getElementById("p1").style.lineHeight = "3";
/*jQuery*/
$(document).ready(function () {
$("#p2").css({ "line-height": "10px" });
$("#p3").css({ "line-height": "150%" });
});
</script>
</body>
</html>