Try This
<body style="z-index: 1; left: 0px; top: 0px; position: absolute; height: 22px; width: 757px">
<form id="form1" runat="server">
<iframe id="frmDoc" runat="server" style="width:800px;height:600px"></iframe>
</form>
</body>
.cs
protected void Page_Load(object sender, EventArgs e)
{
frmDoc.Attributes.Add("src", "http://localhost/docs/test.doc");
}