Custom URL Routing in Global.asax

www.sitefinity.com/.../adding-custom-route-for-static-web-forms-in-sitefinity-sites

I applied this method, but I can't reach the page. 

System.Web.Routing.RouteTable.Routes.MapPageRoute("CustomPageRoute", "customroute","~/CustomPage");

when I write the www.blabla.com/customroute to the browser

IIS can't find the page. But I have a page with name CustomPage in my CMS. I'm creating page using CMS. I mean I dont have a page in my folders with name CustomPage.aspx, but I have page in CMS with this name that is CustomPage, its url is www.blabla.com/custompage .

How can I route my urls ? 

Any luck on resolving this issue?