web services i

this prog shows error..--its for testing the web service in browser
plz give me solution

my code is
---------------
<%@ Webservice Language="c#" class="mathc" %>
using System.Web.Services

Public Class mathc
{
[WebMethod()]
Public int sum(int a,int b)
{
int res=a+b;
return(res);
}

Public int mult(int a,int b)
{
int res=a*b;
return(res);
}
}

shows error
----------------
Server Error in '/' Application. Compilation Error Description: An error occurred during the compila ...