Parent page
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="txtName" ClientIDMode="Static" runat="server" />
</div>
</form>
<script type="text/javascript">
window.open("ChildPage.aspx");
</script>
</body>
Child page
<body>
<form id="form1" runat="server">
<div>
</div>
</form>
<script type="text/javascript">
if (window.opener) {
var txt = window.opener.document.getElementById("txtName");
if (txt) {
txt.value = "Hello from child";
}
}
</script>
</body>
Note that this will work in Chrome and FireFox, but it will only work in IE if the site is in non-protected mode. If the site is a local intranet it should be in non-protected mode automatically, but if not you'll have to add the site to your list of trusted sites. To pre-empt your next questions, no you can't do this without that being configured, and no you can't force IE to trust your site.