实现两种浏览器都可用的属性选择器,实现input的submit风格：
/* For firefox */
input[type="submit"] {
width: 100px;
}
/* For IE */
input {
width: expression(( type == "submit") ? "100px" : "" );
}
/* For firefox */
input[type="submit"] {
width: 100px;
}
/* For IE */
input {
width: expression(( type == "submit") ? "100px" : "" );
}