ASP.NET Page Design Problem

Sir, I am a bit confused of Page designing Pattern in ASP.NET.

My page Design is visible in Design time. But in runtime, none of them is visible

See the web Page view in Design time:-

And in Runtime, here is the view:-

I here giving my html and CSS code.

1) CSS

body
{

}
.Header//header picture
{
    width:1000px;
    height:195px;

}

.p1// paragraph written
{
    width:1000px;
    height:90px;
    margin-top:10px;
    background-color:#009999;



}
#wrapper// the orange colored portion
{
    width:1000px;
    height:600px;
    background-color:#FF9933;

}
.LoginBox // the login div
{
    width:400px;
    height:150px;
    padding:10px 80px auto 20px;
    margin-left:180px;
    margin-bottom:50px;
    margin-right:40px;
    margin-top:100px;
    background-color:#3EA99F;

}

2) HTML

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

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