Problema pagina aspx

[ttttttttttttttt]

Ciao a tutti,
ho il seguente problema aggiungo questo codice in una pagina .aspx

<%
a=Request.ServerVariables("HTTP_SMUSERNAME")

if a <> "" then

response.write ("Ciao")

end if%>

e mi da il seguente errore


Runtime Error

Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.
cation...ecc...ecc



in una normale pagina ASP non ho problemi....
qualcuno mi sa aiutare?

[Raffa62]

hai dichiarato la variabile a ?

dim a as string =Request.ServerVariables("HTTP_SMUSERNAME")