asp, css issue

hi,

I have the selected code:

.imgFairy
{
background-color:Red;
}

<td>

<div>

<div>

<div>

<asp:Image ID="Image2" runat="server" CssClass="imgFairy"
ImageUrl="~/Pics/emothions/fairy32.gif" /> .........................................

 CssClass="imgFairy" doesn't work, why?

can anybody help me?