This sample project demonstrates how to add the HTML5 viewer on the ASPX page and display a simple report. To add the viewer, it is enough to add the StiWebViewer component from the Stimulsoft.Report.Web library:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Show_Report_in_the_Viewer.Default" %>
<%@ Register assembly="Stimulsoft.Report.Web" namespace="Stimulsoft.Report.Web" tagprefix="cc1" %>

<!DOCTYPE html>
<html>
<head runat="server">
	<title>Show report in the Viewer</title>
</head>
<body>
	<form id="form1" runat="server">
		<cc1:StiWebViewer ID="StiWebViewer1" runat="server"
			OnGetReport="StiWebViewer1_GetReport" />
	</form>
</body>
</html>

To display the report, you should add the OnGetReport event, in which you need to load the report and, if required, to register the data:
protected void StiWebViewer1_GetReport(object sender, Stimulsoft.Report.Web.StiReportDataEventArgs e)
{
	string reportPath = Server.MapPath("Reports/SimpleList.mrt");
	StiReport report = new StiReport();
	report.Load(reportPath);
	
	string dataPath = Server.MapPath("Data/Demo.xml");
	DataSet data = new DataSet();
	data.ReadXml(dataPath);
	report.RegData(data);
	
	e.Report = report;
}

In the screenshot below you can see the result of the sample code:

Show Report in the Viewer