Tracing and Listners Question

I am trying to learn about tracing and listeners etc but am having a bit of trouble getting it to work.
I have this in my web config file:


--Other web config stuff here--
 
   
   
                    switchName="mySwitch"
              switchType="System.Diagnostics.SourceSwitch" >
       
         
                      type="System.Diagnostics.DelimitedListTraceListener"
            delimiter="|"
            initializeData="textlog.txt"
            traceOutputOptions="ProcessId, DateTime" />
       
     
   
   
     
   
 
 
And this is the code behind and aspx page.
        protected void Page_Load(object sender, EventArgs e)
        {
            TraceSource source = new TraceSource("mySource");
            source.TraceEvent(TraceEventType.Verbose, 0, "Information Message");
        }
However, when I run the page, I don't get a log file generated.
Can someone please explain why and how?
Thanks
Jeff