Find HTML DIV element in Master Page from Content Page in ASP.Net

Hi

I have MasterPage.master and 3 page that use this masterpage

1-home.aspx

2-product.aspx

3-information.aspx

in masterpage I defive 3 DIV

 <div id="Home" runat="server"></div>
 <div id="Product" runat="server"></div>
 <div id="Information" runat="server"></div>

I want in Home.aspx it change <div id="Home"> Background's image so I wrote below code in home.aspx behind code:

Home.Style["background-image"]=Page.ResolveUrl("~/Images/Extra/H.jpg");

but this error happen:

the name Home doesn't exist in the current context

I think it happen becuse I define div in masterpage not in home.aspx so if I want do it what should I do?

Best regards

Neda