How to print asp.net panel contents using javascript

In this article explained how to print the contents of ASP.Net Panel control using JavaScript.
< html xmlns="http://www.w3.org/1999/xhtml">
< head>
< title>< /title >
        < script type = "text/javascript">
        function PrintPanel() {
        var panel = document.getElementById("ctl00_ContentPlaceHolder1_Panel1<%=Panel1.ClientID %>");
        var printWindow = window.open('', '', 'height=400,width=800');
        printWindow.document.write('');
        printWindow.document.write('');
        printWindow.document.write(panel.innerHTML);
        printWindow.document.write('');
        printWindow.document.close();
        setTimeout(function () {
                                                printWindow.print();
                                            }, 500);
        return false;
        }
        < /script>
< /head>
< body>
        < form id="form1" >
        < asp : Panel id="Panel1" >
                < span style="font-size: 10pt; font-weight:bold; font-family: Arial">HI ,
                    This is < span style="color: #18B5F0">EasyWay Programming. < /span>
                    EasywayProgramming.com
                    easywayprogramming.blogspot.in < /span>
        < /asp:Panel>

        < asp:Button ID="btnPrint" Text="Print" OnClientClick = "return PrintPanel();" />
        < /form>
< /body>
< /html>

In the above HTML Markup has an ASP.Net Panel control Panel1 whose contents needs to be printed and an ASP.Net Button btnPrint which has an OnClientClick event which will call the JavaScript method PrintPanel() to print the contents of the Panel