Try here

You'll need a few lines in web.config

    <section name="log4net" requirePermission="false" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />

just above </configSections>

then

  <log4net>
    <appender name="Console" type="log4net.Appender.ConsoleAppender">
      <layout type="log4net.Layout.PatternLayout">
        <!-- Pattern to output the caller's file name and line number -->
        <conversionPattern value="%-5level [%thread] (%file:%line) - %message%newline" />
      </layout>
    </appender>
    <appender name="RollingFile" type="log4net.Appender.RollingFileAppender">
      <file value="DotNetNuke48.log" />
      <appendToFile value="true" />
      <maximumFileSize value="100KB" />
      <maxSizeRollBackups value="2" />
      <layout type="log4net.Layout.PatternLayout">
        <!--
        <conversionPattern value="%-4timestamp %level [%thread] %logger - %message%newline" />
        -->
        <conversionPattern value="%date %level %logger - %message%newline" />
      </layout>
    </appender>
    <root>
      <!-- Logger Options
      ALL; DEBUG; INFO; WARN; ERROR; FATAL; OFF
      -->
      <level value="DEBUG" />
      <appender-ref ref="Console" />
      <appender-ref ref="RollingFile" />
    </root>
  </log4net>

just after </dotnetnuke>

In your vb file add

Imports log4net
Imports log4net.Config

and

    Friend Shared ReadOnly log As ILog = LogManager.GetLogger(GetType(View))

    Private Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init
        log4net.Config.XmlConfigurator.Configure()
    End Sub

The where you want messages logged :

 log.Debug("Panel visibility set")