请问怎么修改网页顶部背景的宽度 [复制链接]

@import url(/e/css/comm.css);
@import url(/e/css/focus.css);
@import url(diy.css);

/*网站基础样式*/

html{-webkit-text-size-adjust:none;}
body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,code,form,fieldset,legend,input,textarea,th,td,p,blockquote,hr,button,article,aside,details,figcaption,figure,footer,header,hgroup,menu,nav,section{margin:0px;padding:0px;}
article,aside,details,figcaption,figure,footer,header,hgroup,menu,nav,section{display:block;}
audio,canvas,video{display:inline-block;*display: inline;*zoom:1;}
body{word-wrap:break-word;text-align:center;font:13px/1.8 "微软雅黑",Verdana,Arial,\5b8b\4f53;backgroundF9F9F9 url(/e/css/images/top-bg.jpg) repeat-x top center;}

input,select,textarea,button{font-size:100%;}
table{border-collapse:collapse;border-spacing:0;}
img{border:0;}
li{list-style:none;*margin-left:-1px}
.left{float:left}
.right{float:right}
.clear{display:block;clear:both;font-size:0px;height:0px;line-height:0px;width:0px;margin:0px;padding:0px;overflow:hidden}
a{color666;text-decoration:none;text-decoration:none; outline:none;}
a:hover{colorF58021;text-decoration:none;text-decoration:underline}
a:active{star:expression(this.onFocus=this.blur());}
.page_style{text-align:center;background:url(/e/css/images/logo.jpg) no-repeat top center;}

/*顶部及主菜单样式*/

.top_box{clear:both;width:980px;margin:0px auto 0px auto;}
.top_box .logo{float:left;text-align:left;padding:40px 0 0px 50px;}
.top_box .topcontent{display:block;text-align:center;height:383px;}

.menu_style_homepage{float:left;text-align:center;width:90px;}
.menu_style_homepage a.menu{padding-left:0px;}
.menu_style{float:left;text-align:center;width0px;background:url(/e/css/images/nav_line.png) no-repeat left 8px;}

a.menu{display:block;line-height:43px;colorffffff;text-decoration:none;text-align:center}
a.menu:hover{colorFFFFCC;text-decoration:none;}

.menu_current a.menu{display:block;}

这是style.css的代码，现在网页导航是显示器有多宽就显示多长，请问如何改成980px宽？就是和网页一样宽，谢谢。