Adding tracelistener to web.config
You should use system.diagnostics section.Here's example from MSDN for text file:
<configuration> <system.diagnostics> <trace autoflush="false" indentsize="4"> <listeners> <add name="myListener" type="System.Diagnostics.TextWriterTraceListener" initializeData="TextWriterOutput.log" /> <remove name="Default" /> </listeners> </trace> </system.diagnostics></configuration>This is for system events log: http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlogtracelistener.aspx