为什么font-family和字体大小无法使用此css代码？
.content_box { float:left; margin-left:41px; width:265px; font:Arial, Helvetica, sans-serif; }
.content_box h2 { color:#585858; font:bold 25px; margin-bottom:20px; }
.content_box p { color:#4F4F4F; font:12px/1.8em; margin-top:18px; }
.content_box > a { background:url("../images/readmore.jpg") no-repeat top left;
color:#6C6C6C; display:block; font:12px "Times New Roman", Times, serif;
height:29px; margin-top:15px; padding-top:7px; text-align:center;
text-decoration:none; text-transform:uppercase; width:100px;
}
.content_box ul { margin-left:15px;margin-top:3px; list-style:disc inside none;}
.content_box li { border-bottom:1px dotted; list-style-image:url("../images/arow.jpg");
margin-bottom:7px; }
.content_box li a { color:#0F4DB6; font:12px; text-decoration:none; }