Don’t use mappath – you don’t need the server-side file mapping. What you want to use would be either Control.ResolveUrl() or Url.Content() if you are on MVC.
wwb_99: i am using ResolveClientUrl and it worked for me. Hope i am not breaking any thing classic .net rules (don’t have much experience with classic .net).
This was on the CMS side and we are using Kentico (:.