怎么我的文本框是靠左的，怎样才能让他居中

*{  
  margin:0;
padding:0;
list-style-type:none;
font-size:13px;
font-family:'Helvetica Neue',Helvetica,Arial,Sans-serif;
}
body { 
background-image: url(images/mybody_bg.jpg);
}
 #all_wrap {
width: 958px;
margin: 0px auto;
background-image: url(images/mybody_main_bg.gif);
}
#header h1 {
font-size: 36px;
line-height:70px;
}
#header {
margin: 0px auto;
width: 916px;
}
#content {
margin: 0px auto;
width: 916px;
border: 1px solid #3683D8;
}
.item {
margin: 0px auto;
width: 896px;
border-bottom-width: 1px;
border-bottom-style: dashed;
border-bottom-color: #900;
clear:both;
}
.a {
float: left;
width:60px;
margin-top:5px;
}

/*留言列表*/
.n,.t,.m{
line-height:30px;
}
.n {
float: left;
color:#00F;
padding-right:5px;
}
.t{
color:#666;
}
.o {
float: right;
}
.m{
padding-left:60px;
padding-right:30px;
word-break:break-all;
}

/*新留言表单*/
.form_line{
clear:both;
margin-top:10px;
}
.form_box { 
margin: 0px auto;
width: 890px;
}
.form_text {
float: left;
width: 80px;
text-align:right;
}
#form_select_avater label {
width: 60px;
display: block;
float: left;
text-align: center;
cursor: pointer;
}
.form_input textarea {
width: 500px;
height: 70px;
}
#submit_0{
width:100px;
height:30px;
}
#footer{
margin: 0px auto;
width: 896px;
}
.footer_message {
line-height: 40px;

}
.pagination {
text-align: center;
margin:10px auto 10px auto;
}
.pagination a {
display: inline-block;
border: 1px solid #00F;
padding-right: 8px;
padding-left: 8px;
padding-top: 2px;
padding-bottom: 2px;
text-decoration: none;
color: #900;
margin-right: 4px;
}
.pagination a:hover{
border-color:#F0F;
color:#000;
}
.login_button {
float: right;
}
#submit_1 {
width: 60px;
}
.login_form form label {
float: left;
display: block;
width: 220px;
}
.login_form {
padding-top: 20px;
}
.login_form form {
display: block;
border: 1px dashed #F0F;
width:520px;
padding-top:10px;
padding-bottom:10px;
padding-left:3px;
}
.welcome_info {
color: #900;
float: right;
}
.r {
color: #F00;
}
.retime{
color:#666;
}
.login_button a{
text-decoration:none;
}
#login_form{
display:none;}


------解决方案--------------------
文字？

.form_input textarea {
width: 500px;
height: 70px;
}

加上
text-align: center;

以后css 问题请发到相应的板块

------解决方案--------------------
.文本框样式｛width:100px;margin:0 auto;｝