Click on the OK Button:-
Now you will see a new from like this :-
This is the Source Code window and in this page you will se this code.
First you have to learn XML and HTML to work with ASP .NET.
I have used <"text"> to make the text as comment this is the way to make comment in this code.
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>Type your webpage title here</title> <Here you can specify your page title in between title tag>
</head>
<body>
<form id="form1" runat="server">
<div>
<"In between div tags you can manage your web controls like buttons, labels, picture
Box, ImageMap etc">
</div>
</form>
</body>
</html>
See here is a tab named Design in the bottom of this page