inheriting toolbar control

[???Q]

Hi ...

I trying to inherit from toolbar .


'==clsMizUwg.vb==

<Assembly: TagPrefix("ctlmizUwg.nmmizUwg", "miz")>

Namespace nmmizUwg

<ToolboxData("<{0}:clsToolBar runat=server></{0}:clsToolBar>")> _
Public Class clsToolBar
Inherits Microsoft.Web.UI.WebControls.Toolbar
End Class
End Namespace

When I drag into aspx form and add some button , code generate like this ,
I'd like to know why ToolbarButton got the prefix <iewc: instead of <miz:
thanks for help ..

<miz:clstoolbar id="ClsToolBar1" style="Z-INDEX: 102; LEFT: 256px;
POSITION: absolute; TOP: 80px"
runat="server" Height="104px" Width="240px">
<iewc:ToolbarButton Text="Button"></iewc:ToolbarButton>
<iewc:ToolbarButton Text="Button"></iewc:ToolbarButton>
</miz:clstoolbar>