我通过设置这样的边距并使内部空间(框+填充)与字体大小相同来完成这项工作。
http://jsbin.com/unera3/5/edit
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>Backbone: Tody</title>
<style>
.delete {
-moz-border-radius: .75em;
-webkit-border-radius: .75em;
width: 1.4em;
height: 1.4em;
text-align: center;
line-height: 1.4em;
vertical-align:middle
font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
font-size: 14px;
font-weight: bold;
color: white;
background-color: gray;
cursor: pointer;
}
.delete:before {
content: "\2715";
/* content: "\00D7"; */
}
.delete:hover {
background-color: red;
}
</style>
</head>
<body>
<div class="delete"></div>
</body>
</html>