Edit in JSFiddle

var HtmlBindingModel = function () {
    var self = this;
    self.simpleText = ko.observable("<i>这是一段简单的斜体文本Html</i>");
    self.objectText = {
        firstName: "kai",
        lastName: "cui",
        toString: function () {
            return '<span style="color:blue;">这个对象自己重写了toString(' + this.firstName + ' ' + this.lastName + ')</span>';
        }
    };
    self.objectText2 = {
        firstName: "kai",
        lastName: "cui"
    };
};
ko.applyBindings(new HtmlBindingModel(), document.getElementById("Demo4"));

<h1>演示 KnockOut Html绑定</h1>
<hr />
<ul>
   <li  class="Point">
    4、<b  class="PointTitle">理解<span class="KeyWord">Html</span>绑定</b><br />
        <ul class="PointDesc">
            <li>绑定对应元素的innerHTML属性</li>
            <li>如果是ko.observable的，则该绑定是双向的</li>
            <li>如果绑定的不是一个整数或者字符，比如对象，则会调用对象的toString()方法</li>
        </ul>
        <div  class="PointDemo" id="Demo4">
            <span data-bind="html: simpleText"></span><br />
            <span data-bind="html: objectText"></span><br />
            这个对象没有定义toString<span data-bind="html: objectText2"></span>
        </div>
        <!--下面写一些特殊的提示信息-->
        <div class="PSFrame">
        注意绑定可以是object,会调toString()
        </div>
        <hr />
    </li>
</ul>
<hr />

/*Demo�ļ���ʽ*/
body
{
    background-color: #e3e5d4;
}
/*  ֪ʶ��    */
.Point
{
    margin: 20px,0,0,0;
}
/*  ֪ʶ�����    */
.PointTitle
{
    color:#0d8d0d;
}
/*  �ؼ���    */
.KeyWord
{
    color:Red;
}
/*  ֪ʶ������    */
.PointDesc
{
    font-family: Arial;
    font-size: 15px;
    color:#09acb8;
}
.PointDesc li
{
    margin: 10px,0,0,0;
}
/*  ֪ʶ��Demo���    */
.PointDemo
{
    border-style:double; 
    border-color:#dcd559;
    min-height:100px;
    font-family: Corbel;
    font-size: 20px;
    color: #00174f;
}
/*  ��Ҫ������ʾ����Ϣ���    */
.PSFrame
{
    border-style: dashed; 
    border-color:#78e6ef;
    font-family: Corbel;
    font-size: 20px;
    font-style:italic;
    color: #b86c00;
}
/*  ������ʾ    */
.error {
    color:Red;
    
}
/*  **********************************************************    */
/*��Ҫǿ������ʽ*/
.Notice
{
    font-weight: bold;
    font-family:Bodoni MT Black;
    color: #cd0707;
}

/*  **********************************************************    */
/*�������ʽ*/
input[type="text"]
{
    min-width:250px;
}
select
{
    min-width:400px;
}