http://jsfiddle.net/gh/gist/library/pure/7ebf6181ab13a02951c0/

fiddle.css

@import url('https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css');
.badge-danger { background-color: #d9534f !important; }

fiddle.html

<div class="container">

  <form class="form-horizontal">
    <h1>Form</h1>

    <ul class="nav nav-tabs" style="margin-bottom: 15px;">
      <li role="presentation" class="active"><a href="#tab1" data-bind="click: clickTab1">Tab1 <span class="badge badge-danger" data-bind="errorCount: tab1.errors().length"></span></a></li>
      <li role="presentation"><a href="#tab2" data-bind="click: clickTab2">Tab2 <span class="badge badge-danger" data-bind="errorCount: tab2.errors().length"></span></a></li>
      <li role="presentation"><a href="#tab3" data-bind="click: clickTab3">Tab3 <span class="badge badge-danger" data-bind="errorCount: tab3.errors().length">4</span></a></li>
      <li role="presentation" class="pull-right">
        All Erros <span class="badge badge-danger" data-bind="errorCount: allTabErrors"></span>
      </li>
    </ul>

    <div class="tab-content">

      <!-- ko with: tab1 -->
      <div role="tabpanel" class="tab-pane active" id="tab1">
        <div class="form-group">
          <label class="col-sm-2 control-label" for="inputEmail">Email</label>
          <div class="col-sm-10" data-bind="validationElement: email">
            <input type="text" id="inputEmail" class="form-control" placeholder="Email" data-bind="textinput: email"/>
            <p class="text-danger" data-bind="validationMessage: email"></p>
          </div>
        </div>
        <div class="form-group">
          <label class="col-sm-2 control-label" for="inputPassword">Password</label>
          <div class="col-sm-10" data-bind="validationElement: password">
            <input type="password" id="inputPassword" class="form-control" placeholder="Password" data-bind="textinput: password"/>
            <p class="text-danger" data-bind="validationMessage: password"></p>
          </div>
        </div>
      </div>
      <!-- /ko -->

      <!-- ko with: tab2 -->
      <div role="tabpanel" class="tab-pane" id="tab2">
        <div class="form-group">
          <label class="col-sm-2 control-label" for="input1">Input1</label>
          <div class="col-sm-10" data-bind="validationElement: input1">
            <input type="text" id="input1" class="form-control" placeholder="input1" data-bind="value: input1"/>
            <p class="text-danger" data-bind="validationMessage: input1"></p>
          </div>
        </div>
        <div class="form-group">
          <label class="col-sm-2 control-label" for="input2">Input2</label>
          <div class="col-sm-10" data-bind="validationElement: input2">
            <input type="text" id="input2" class="form-control" placeholder="input2" data-bind="value: input2"/>
            <p class="text-danger" data-bind="validationMessage: input2"></p>
          </div>
        </div>
        <div class="form-group">
          <label class="col-sm-2 control-label" for="input3">Input3</label>
          <div class="col-sm-10" data-bind="validationElement: input3">
            <input type="text" id="input3" class="form-control" placeholder="input3" data-bind="value: input3"/>
            <p class="text-danger" data-bind="validationMessage: input3"></p>
          </div>
        </div>
      </div>
      <!-- /ko -->

      <!-- ko with: tab3 -->
      <div role="tabpanel" class="tab-pane" id="tab3">
        <div class="form-group">
          <label class="col-sm-2 control-label">Range</label>
          <div class="col-sm-2" data-bind="validationElement: rangeMin">
            <input type="text" id="inputRangeMin" class="form-control" placeholder="min" data-bind="textinput: rangeMin"/>
            <p class="text-danger" data-bind="validationMessage: rangeMin"></p>
          </div>
          <span class="pull-left">
            〜
          </span>
          <div class="col-sm-2" data-bind="validationElement: rangeMax">
            <input type="text" id="inputRangeMax" class="form-control" placeholder="max" data-bind="textinput: rangeMax"/>
            <p class="text-danger" data-bind="validationMessage: rangeMax"></p>
          </div>
        </div>
      </div>
      <!-- /ko -->

    </div>

    <div class="form-group well well-lg" >
      <div class="col-sm-offset-2 col-sm-10">
        <button type="submit" class="btn btn-primary" data-bind="enable: allTabErrors() == 0">Submit</button>
        <button type="button" class="btn">Cancel</button>
      </div>
    </div>

  </form>

</div>

fiddle.js

$(function() {
    ko.bindingHandlers['errorCount'] = {
        init: function (element, valueAccessor) {
            var value = ko.utils.unwrapObservable(valueAccessor());
        },
        update: function (element, valueAccessor, allBindings, viewModel, bindingContext) {
            var value = ko.utils.unwrapObservable(valueAccessor());
            if(value == 0){
                $(element).removeClass('badge-danger').text('OK');
            } else {
                $(element).addClass('badge-danger').text(value);
            }
        }
    };

    ko.validation.rules['rangeMinMax'] = {
        validator: function (val, params) {
            var min = ko.validation.utils.getValue(params[0]);
            var max = ko.validation.utils.getValue(params[1]);
            if (!ko.validation.utils.isEmptyVal(min) &&
               !ko.validation.utils.isEmptyVal(max) &&
                ko.validation.utils.isNumber(min) &&
                ko.validation.utils.isNumber(max)) {
                return parseInt(min, 10) < parseInt(max, 10);
            } else {
                return true;
            }
        },
        message: 'message'
    };
    ko.validation.registerExtenders();

    function tab1ViewModel() {
        var self = this;
        self.email = ko.observable().extend({
            required: {
                message: 'required'
            },
            email: {
                message: 'invalid format'
            }
        });
        self.password = ko.observable().extend({
            required: {
                message: 'required'
            },
            minLength: {
                params: 6,
                message: 'too short'
            }
        });
    }

    function tab2ViewModel() {
        var self = this;
        self.input1 = ko.observable();
        self.input2 = ko.observable();
        self.input3 = ko.observable();

        self.hasValue = ko.computed(function() {
            return (self.input1() || self.input2() || self.input3());
        });

        self.input1.extend({
            required: {
                message: 'required',
                onlyIf: function () {
                    if (self.hasValue()) {
                        return true;
                    }
                    return false;
                }
            }
        });
        self.input2.extend({
            required: {
                message: 'required',
                onlyIf: function () {
                    if (self.hasValue()) {
                        return true;
                    }
                    return false;
                }
            }
        });
        self.input3.extend({
            required: {
                message: 'required',
                onlyIf: function () {
                    if (self.hasValue()) {
                        return true;
                    }
                    return false;
                }
            }
        });
    }

    function tab3ViewModel() {
        var self = this;
        self.rangeMin = ko.observable();
        self.rangeMax = ko.observable();

        self.rangeMin.extend({
            number: {
                message: "invalid format"
            },
            rangeMinMax: {
                params: [self.rangeMin, self.rangeMax],
                message: "invalid range"
            }
        });
        self.rangeMax.extend({
            number: {
                message: "invalid format"
            },
            rangeMinMax: {
                params: [self.rangeMin, self.rangeMax],
                message: "invalid range"
            }
        });
    }

    function myViewModel() {
        var self = this;
        self.tab1 = ko.validatedObservable(new tab1ViewModel());
        self.tab2 = ko.validatedObservable(new tab2ViewModel());
        self.tab3 = ko.validatedObservable(new tab3ViewModel());
        self.allTabErrors = ko.computed(function() {
            return parseInt(self.tab1.errors().length, 10) +
                    parseInt(self.tab2.errors().length, 10) +
                    parseInt(self.tab3.errors().length, 10);
        }, self);

        self.clickTab1 = function(data, event) {
            event.preventDefault()
            $(event.target).tab('show')
        }
        self.clickTab2 = function(data, event) {
            event.preventDefault()
            $(event.target).tab('show')
        }
        self.clickTab3 = function(data, event) {
            event.preventDefault()
            $(event.target).tab('show')
        }
    }

    ko.validation.init({
        insertMessages: false,
        messagesOnModified: false,
        decorateElement: true,
        errorElementClass: 'has-error'
    });
    var viewModel = ko.validatedObservable(new myViewModel());
    ko.applyBindings(viewModel);
})

fiddle.manifest

name: KnockoutJS Validation Sample 7
authors:
  - laughingman7743
resources:
  - http://knockoutjs.com/downloads/knockout-3.3.0.js
  - http://code.jquery.com/jquery-2.1.4.min.js
  - http://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js
  - http://cdnjs.cloudflare.com/ajax/libs/knockout-validation/2.0.3/knockout.validation.min.js
normalize_css: no
wrap: b
panel_js: 0
panel_css: 0