关于jquery页面自动跳转的问题

<div id="BellPhone">                                <br>                                <span id="PortInPstnLabel">住址电话：</span>                                <input id="BellPhone1" type="text" style="width: 32px;" size="3" maxlength="3" name="BellPhone1" class="bell" >-                                <input id="BellPhone2" type="text" style="width: 32px;" size="3" maxlength="3" name="BellPhone2" class="bell">-                                <input id="BellPhone3" type="text" style="width: 40px;" size="4" maxlength="4" name="BellPhone3" class="bell">                            </div>

 $(".bell").keyup(function () {
        var length = $(this).val().length;
        if (length == "3") {
            $(this).next(".bell").focus();
        }
    })