Is the value "username" correctly being passed in the querystring. The statement "Request.QueryString["username"].ToString();" is not getting the value from the querystring hence the error

function OpenFloatingForm(target, id, SecondId) { var pnlId = ""; var page = ""; var maskId = ""; var z_index = ""; var margin = 30; switch (target) { case "Donor": pnlId = "#pnlFloating1"; page = "DonationForm.aspx"; maskId = "#mask1"; z_index = "100"; break; case "Payment": pnlId = "#pnlFloating1"; page = "PaymentRealizationDetailForm.aspx"; maskId = "#mask1"; z_index = "100"; break; } var maskHeight = $(document).height(); var maskWidth = $(window).width(); //Set height and width to mask to fill up the whole screen $(maskId).css({ 'width': maskWidth + 'px', 'height': maskHeight + 'px', 'z-index': z_index }); $(maskId).show(); var scrollTop = $(document).scrollTop(); var docWidth = document.body.clientWidth; var docHeight = $(window).height(); $(pnlId).width(docWidth - 2 * margin); $(pnlId).height(docHeight - (margin * 2)); $(pnlId).css('left', margin); $(pnlId).css('top', margin + scrollTop); var frame = $(pnlId).find('iframe'); frame.attr('src', "blank.htm"); frame.width($(pnlId).width()); frame.height($(pnlId).height() - 25); var param2 = (SecondId > 0) ? "&PaymentID=" + SecondId : ""; frame.attr('src', page + "?DonorID=" + id + param2); $(pnlId).fadeIn('slow', function () { }); return false; }