day3--css水平居中(bootstrap)

   <div >
        <br />
        <br />
        <div class="input-group input-group-lg" style="margin:0 auto; width:350px;">
            <span class="input-group-addon" id="sizing-addon1">手机号</span>
            <input type="text" class="form-control " aria-describedby="sizing-addon1" oninput="if(value.length>11) value=value.slice(0,11)" name="phone" value=""> <!-- onblur="check(this.value)" -->
        </div>
        <br />
        @*<div class="input-group input-group-lg" style="margin:0 auto; width:300px;">
                <span class="input-group-addon" id="sizing-addon1">公&nbsp&nbsp&nbsp&nbsp司</span>
                <select class="form-control"  id="selectCompany" name="company"></select>
            </div>*@
        <br />

        <div class="input-group input-group-lg " style="margin:0 auto; width:350px;">
            <span class="input-group-addon" id="sizing-addon1">密&nbsp&nbsp&nbsp码</span>
            <input type="password" class="form-control" aria-describedby="sizing-addon1" name="pasword">
        </div>
        <br />
        <div style="margin:0 auto; width:350px;text-align:center;">
            <p class="inline" style="color:red;">*首次登录需先设置密码</p>
        </div>
        <br />
        <br />

设置 

width:350px;
是关键