window.parent.document.body is not working in IE11

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ASP.NET

Hi,
The below code is working fine in IE8,IE9 but it is not working in IE11 as

function CloseWinAndSave(existingVendor) {
var parent = window.parent.document.body;
if (existingVendor=="True") {
parent.all["divDdl"].style.display = "block";
parent.all["divTxt"].style.display = "none";

}
else {
parent.all["divDdl"].style.display = "none";
parent.all["divTxt"].style.display = "block";

}
window.parent.closeDialog();
return false;
}

this code is in child window and here 'divDdl' tag is in parent windows so how can we achieve this please suggest.