当鼠标移到上面字消失，移出又出现的效果代码

 <asp:TextBox ID="txtapplMemo" runat="server" Height="100px" Width="442"
      MaxLength="500" TextMode="MultiLine" value="备注：" onfocus="if(value=='备注：') {value=''}" onblur="if(value=='') {value='备注：'}"></asp:TextBox>