See which ASP.NET version a site is running on

The following code shows which version of ASP.NET is used and whether Integrated or Classic pipeline is used.

<%@ Page Language="C#" %>
<%
string pipeline = "";           
if(HttpRuntime.UsingIntegratedPipeline == true) {
    pipeline = "Integrated Pipeline mode";
}
else {
    pipeline = "Classic Pipeline mode";
}
%>
<p>Your site runs on: <b><% Response.Write(Request.ServerVariables["SERVER_SOFTWARE"]); %></b></p>
<p>Your application pool runs on <b><% Response.Write(pipeline); %></b> and .NET version: <b><% Response.Write(System.Environment.Version); %></b></p>

Copy this code into a file named version.aspx, place the file on your web space and open it in your browser.

If you want to run ASP.NET 4.5.1 or later, you can simply deploy it yourself on the server, as this is best practice.