ASP Rewrite url path

[mido221]

I get an error on rewitting url by:\[code\] if (!IsPostBack) { string req = Request.QueryString["prodID"]; if (req != null) { int prodID = int.Parse(Request.QueryString["prodID"]); koszyk.Dodaj(prodID); //del prodID from url: string url = Request.Url.AbsolutePath; System.Web.HttpContext.Current.RewritePath(url, "", ""); } }\[/code\]error message:Virtual Path performs mapping to another application, which is prohibited.FULL LOG: System.Web.VirtualPath.FailIfNotWithinAppRoot() +3116542 System.Web.HttpContext.RewritePath(VirtualPath filePath, VirtualPath pathInfo, String queryString, Boolean setClientFilePath) +63 System.Web.HttpContext.RewritePath(String filePath, String pathInfo, String queryString) +48 Zakupy.Page_Load(Object sender, EventArgs e) in c:\Documents and Settings\Informatyk\Pulpit\NAI\Modu?11\Problem1, 2, 3\Zakupy.aspx.cs:30 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35 System.Web.UI.Control.OnLoad(EventArgs e) +91 System.Web.UI.Control.LoadRecursive() +74 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207This occurs when I want to add something to the basketany ideas?