function Button1_onclick() {
var doc = window.frames["iframepage"];
doc.window.location.href = "HTMLPage3.htm";
}
<body>天涯
<iframe id="iframepage" name="iframepage" height="50px" scrolling="no" src="HTMLPage2.htm" width="100%" frameborder="0"></iframe>
dadi
<input id="Button1" type="button" value="button" onclick="return Button1_onclick()" />
</body>
二、超鏈接
var action = "HelpList.aspx";
$("#search").attr("href", action);
<a id="search" target="iframepage" href="#">
<iframe id="iframepage" name="iframepage" height="50px" scrolling="no" src="HTMLPage2.htm" width="100%" frameborder="0"></iframe>