求一段javascript 代码
<asp:DataList ID="dtlOrganization" runat="server" RepeatColumns="3" RepeatDirection="Horizontal"
CssClass="couse_listtab" DataKeyField="fMyFileGuid" OnEditCommand="Edit" OnDeleteCommand="Delete"
Width="300px">
<ItemTemplate>
<table>
<tr>
<td style="width:20px">
<asp:Image ID="img" runat="server" ImageUrl='<%# Eval("fImage") %>'></asp:Image>
</td>
<td style="width:250px">
<span id="spanSelect" class="div_FolderFile" onmouseover ="onmouseout('td1')" onmouseout="javascript:this.className='div_FolderFile';"
runat="server">
<table>
<tr>
<td>
<asp:HyperLink ID="hlkOrganization" runat="server" Text='<%# Eval("fName") %>' NavigateUrl='<%# Eval("fUrl") %>' Target="_blank"></asp:HyperLink></td>
<td nowrap id="td1" runat="server">
<asp:ImageButton ID="imgEdit" runat="server" ImageAlign="absMiddle" ImageUrl="~/CourseBuilde/images/course_docu_edit_03.gif"
CommandName="Edit"></asp:ImageButton>
<asp:ImageButton ID="imgDelete" runat="server" ImageAlign="absMiddle" ImageUrl="~/CourseBuilde/images/course_docu_edit_05.gif"
CommandName="Delete" OnClientClick="javascrpt:return confirm('确定要删除吗')"/>
<asp:HiddenField ID="txtfMyFolderGuid" runat="server" Value='<%# Eval("fMyFolderGuid") %>' />
<asp:HiddenField ID="txtfMyFileGuid" runat="server" Value='<%# Eval("fMyFileGuid") %>' />
</td>
</tr>
<tr>
<td nowrap>
<asp:HyperLink ID="HyperLink1" runat="server" Text='<%# Eval("fName1") %>' NavigateUrl='<%# Eval("fUrl") %>'></asp:HyperLink>
<span class="all_couse_01">
<asp:Label runat="server" ID="lblCountPublicSubject" Text='<%# Eval("fProperty") %>'></asp:Label>
</span>
</td>
<td id="td2" style="display:none" runat="server">
<asp:CheckBox ID="chbSelect" runat="server" CssClass='<%# Eval("fMyFileGuid") %>'/></td>
</tr>
</table>
</span>
</td>
</tr>
</table>
</ItemTemplate>
<ItemStyle Width="200px"/>
</asp:DataList>
我想在鼠标在span 区域时,td1 和 td2 能 显示 离开则 隐藏