Question

var gd = new GridView
{
    DataSource = li,
    AutoGenerateColumns = true,
};

gd.DataBind();

if (gd.Rows.Count > 0)
{
    HttpContext.Current.Response.Clear();
    HttpContext.Current.Response.Buffer = true;
    HttpContext.Current.Response.AddHeader("content-disposition", "attachment;filename=" + "List" + DateTime.Now.ToString("dd.MM.yyyy") + ".doc");
    HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
    HttpContext.Current.Response.ContentType = "application/ms-word";
    HttpContext.Current.Response.Charset = "UTF-8";
    HttpContext.Current.Response.BinaryWrite(System.Text.Encoding.UTF8.GetPreamble());

    var oStringWriter = new System.IO.StringWriter();
    var oHtmlTextWriter = new HtmlTextWriter(oStringWriter);

    gd.RenderControl(oHtmlTextWriter);
    HttpContext.Current.Response.Output.Write(oStringWriter.ToString());
    HttpContext.Current.Response.Flush();
    HttpContext.Current.Response.End();
}

ERROR (lines wrapped):

Sys.WebForms.PageRequestManagerParserErrorException: 
Sys.WebForms.PageRequestManagerParserErrorException:
The message received from the server could not be parsed.' when calling method:
[nsIDOMEventListener::handleEvent]
[Break On This Error]   

Filtered chrome url chrome://firebug/content/net/spy.js

spy.js (line 807)
<System>

Answer 1

Try this:

Response.ContentType = "application/octet-stream"