960px网格系统 - 图像显示问题

Question

我正在使用960px网格系统来显示基本网页，它由4个不同的图像组成。我正试图让他们所有人在他们组成网页的时候很好地坐在彼此之上。然而，它们只是显示在一个图像列表中，一个在另一个上面，依此类推。任何帮助将不胜感激！这是迄今为止的代码：

CSS：

    /* IDs 
----------------------------------------------------------------------------------------------------*/

#background {

    border-collapse: collapse;
    z-index: 1; 
    position: absolute;

}

#foreground {

    border-collapse: collapse;
    z-index: 10; 
    position: absolute;

}

body {
  min-width: 960px;
}

/* `Container
----------------------------------------------------------------------------------------------------*/

.container_12 {
  margin-left: auto;
  margin-right: auto;
  width: 960px;
}

/* `Grid >> Global
----------------------------------------------------------------------------------------------------*/

.grid_1,
.grid_2,
.grid_3,
.grid_4,
.grid_5,
.grid_6,
.grid_7,
.grid_8,
.grid_9,
.grid_10,
.grid_11,
.grid_12 {
  display: block;
  float: left;
  margin-left: 10px;
  margin-right: 10px;
}

.push_1, .pull_1,
.push_2, .pull_2,
.push_3, .pull_3,
.push_4, .pull_4,
.push_5, .pull_5,
.push_6, .pull_6,
.push_7, .pull_7,
.push_8, .pull_8,
.push_9, .pull_9,
.push_10, .pull_10,
.push_11, .pull_11 {
  position: absolute;
}

/* `Grid >> Children (Alpha ~ First, Omega ~ Last)
----------------------------------------------------------------------------------------------------*/

.alpha {
  margin-left: 0;
}

.omega {
  margin-right: 0;
}

/* `Grid >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .grid_1 {
  width: 60px;
}

.container_12 .grid_2 {
  width: 140px;
}

.container_12 .grid_3 {
  width: 220px;
}

.container_12 .grid_4 {
  width: 300px;
}

.container_12 .grid_5 {
  width: 380px;
}

.container_12 .grid_6 {
  width: 460px;
}

.container_12 .grid_7 {
  width: 540px;
}

.container_12 .grid_8 {
  width: 620px;
}

.container_12 .grid_9 {
  width: 700px;
}

.container_12 .grid_10 {
  width: 780px;
}

.container_12 .grid_11 {
  width: 860px;
}

.container_12 .grid_12 {
  width: 940px;
}

/* `Prefix Extra Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .prefix_1 {
  padding-left: 80px;
}

.container_12 .prefix_2 {
  padding-left: 160px;
}

.container_12 .prefix_3 {
  padding-left: 240px;
}

.container_12 .prefix_4 {
  padding-left: 320px;
}

.container_12 .prefix_5 {
  padding-left: 400px;
}

.container_12 .prefix_6 {
  padding-left: 480px;
}

.container_12 .prefix_7 {
  padding-left: 560px;
}

.container_12 .prefix_8 {
  padding-left: 640px;
}

.container_12 .prefix_9 {
  padding-left: 720px;
}

.container_12 .prefix_10 {
  padding-left: 800px;
}

.container_12 .prefix_11 {
  padding-left: 880px;
}

/* `Suffix Extra Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .suffix_1 {
  padding-right: 80px;
}

.container_12 .suffix_2 {
  padding-right: 160px;
}

.container_12 .suffix_3 {
  padding-right: 240px;
}

.container_12 .suffix_4 {
  padding-right: 320px;
}

.container_12 .suffix_5 {
  padding-right: 400px;
}

.container_12 .suffix_6 {
  padding-right: 480px;
}

.container_12 .suffix_7 {
  padding-right: 560px;
}

.container_12 .suffix_8 {
  padding-right: 640px;
}

.container_12 .suffix_9 {
  padding-right: 720px;
}

.container_12 .suffix_10 {
  padding-right: 800px;
}

.container_12 .suffix_11 {
  padding-right: 880px;
}

/* `Push Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .push_1 {
  left: 80px;
}

.container_12 .push_2 {
  left: 160px;
}

.container_12 .push_3 {
  left: 240px;
}

.container_12 .push_4 {
  left: 320px;
}

.container_12 .push_5 {
  left: 400px;
}

.container_12 .push_6 {
  left: 480px;
}

.container_12 .push_7 {
  left: 560px;
}

.container_12 .push_8 {
  left: 640px;
}

.container_12 .push_9 {
  left: 720px;
}

.container_12 .push_10 {
  left: 800px;
}

.container_12 .push_11 {
  left: 880px;
}

/* `Pull Space >> 12 Columns
----------------------------------------------------------------------------------------------------*/

.container_12 .pull_1 {
  left: -80px;
}

.container_12 .pull_2 {
  left: -160px;
}

.container_12 .pull_3 {
  left: -240px;
}

.container_12 .pull_4 {
  left: -320px;
}

.container_12 .pull_5 {
  left: -400px;
}

.container_12 .pull_6 {
  left: -480px;
}

.container_12 .pull_7 {
  left: -560px;
}

.container_12 .pull_8 {
  left: -640px;
}

.container_12 .pull_9 {
  left: -720px;
}

.container_12 .pull_10 {
  left: -800px;
}

.container_12 .pull_11 {
  left: -880px;
}

/* `Clear Floated Elements
----------------------------------------------------------------------------------------------------*/

/* http://sonspring.com/journal/clearing-floats */

.clear {
  clear: both;
  display: block;
  overflow: hidden;
  visibility: hidden;
  width: 0;
  height: 0;
}

/* http://www.yuiblog.com/blog/2010/09/27/clearfix-reloaded-overflowhidden-demystified */

.clearfix:before,
.clearfix:after,
.container_12:before,
.container_12:after {
  content: '.';
  display: block;
  overflow: hidden;
  visibility: hidden;
  font-size: 0;
  line-height: 0;
  width: 0;
  height: 0;
}

.clearfix:after,
.container_12:after {
  clear: both;
}

/*
  The following zoom:1 rule is specifically for IE6 + IE7.
  Move to separate stylesheet if invalid CSS is a problem.
*/

.clearfix,
.container_12 {
  zoom: 1;
}

HTML：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>Title</title>
    <link rel="stylesheet" type="text/css" href="<%= application.getRealPath("/resources/grid.css") %>">

</head>

<body>

    <!-- Main container -->
    <div class = "container_12" id = "Background">

        <img src = "<%= application.getRealPath("/resources/images/Background.png") %>">

    </div>

    <!-- Foreground container -->
    <div class = "grid_10 prefix_1 suffix_1" id = "Foreground">

        <img src = "<%= application.getRealPath("/resources/images/Foreground.png") %>">

    </div>  

    <!-- Header container -->
    <div class = "grid_8 prefix_2 suffix_2" id = "Header">

        <img src = "<%= application.getRealPath("/resources/images/Header.png") %>">

    </div>

    <div class = "clear"></div>

    <!-- Navigation bar container -->
    <div class = "grid_8 prefix_2 suffix_2" id = "">

        <img src = "<%= application.getRealPath("/resources/images/Navbar.png") %>">

    </div>

</body>

</html>

提前致谢：）