I am just starting to learn jQuery and so I've created the most bare bones sample module for just plain javascript.  I used the Simple Dynamic Module template in VS 2008 for DNN 5.0 and used the View.ascx to place a button and a label within a div.  Later I was going to try substituting jQuery code.

The following works in IE 7 (when I click the button the word 'Hide' disappears).

So what am I doing wrong?

function ShowHide(divName, OnOff) {
    var ele = document.getElementById(divName);
    if (ele != null) {
        if (OnOff == "on")
            ele.style.display = "block";
        else
            ele.style.display = "none";
    }
}

	Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
            Try
                DotNetNuke.Framework.jQuery.RequestRegistration()
                Dim jQueryEthScriptPath As String = Me.TemplateSourceDirectory & "/SomeScript.js"
                Page.ClientScript.RegisterClientScriptInclude("SomeScript", jQueryEthScriptPath)
                If Not Page.IsPostBack Then

                End If
            Catch exc As Exception
                ProcessModuleLoadException(Me, exc)
            End Try
        	End Sub

<input id="Button1" type="button" value="button" onclick="ShowHide('myDiv','off');"/>
<div id="MyDiv">
<asp:Label ID="Label1" runat="server" Text="Hide"></asp:Label>
</div>

In my jQuery tests, I'm trying to get this basic javascript to work and then I'll start referencing the jQuery library.  But maybe I'll be lucky to find someone who already has a very, very simple "click me to hide me" DNN module that uses jQuery and works in both IE and Firefox.  Or maybe there are several gotchas with using basic javascript and I should jump right into jQuery?