연습하기위해 사이트카피를 하고 있는데 header 부분 CSS 작성이 이해가 안되는 부분이 있어서 질문드려요

<div id="top">
    <div class="header">
        <div class="global">
            <div class="content">
                <div class="user">
                    <ul>
                        <li><a href="">Bookmark</a></li>
                    </ul>
                </div>
                <div class="member">
                    <ul id="top_menu">
                        <li><a href="./member/member_form.php">회원가입</a></li>
                        <li><a href="./login/login_form.php">로그인</a></li>
                    </ul>
                </div>
                <div class="head-search">
                    <form action="" method="get" onsubmit="return Hsearch(this);">
                        <input type="hidden" name="sc" value="all">
                        <div class="group">
                            <input type="text" name="sk" class="input" placeholder="검색어를 입력하세요">
                            <input type="submit" name="serch" class="submit" value="검색">
                        </div>
                    </form>
                </div>
            </div>
        </div>

        <div class="head">
            <div class="content">
                <div class="main-title">
                    <a href=""><img src="/img/logo.png" alt="" width="160px"></a>
                </div>
                <div class="nav">
                    <ul>
                        <li class="m1"><a href="">TOP</a></li>
                        <li class="m2"><a href="">DRESS</a></li>
                    </ul>
                </div>
            </div>
        </div>
    </div>

CSS

/* 초기화 */
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {margin: 0; padding: 0; border: 0; font-size: 100%; font: inherit; vertical-align: baseline; box-sizing: border-box; text-decoration: none;}

article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section {display: block;}

body {line-height: 1;}

ol, ul {list-style: none;}

blockquote, q {quotes: none;}

blockquote:before, blockquote:after,
q:before, q:after {content: ''; content: none;}

table {border-collapse: collapse; border-spacing: 0;}

#top {position: relative; min-width: 1380px;}
.content {margin: 0 auto;}

.header {position: relative; width: 100%; padding-bottom: 120px; z-index: 1000;}
.header .global {border-bottom: 1px solid #ddd;}
.header .content {position: relative; width: 1320px; z-index: 5;}
.global .content {height:52px;}
.global .content ul:after {content: ''; display: block; clear: both;}
.global .content ul li {float: left; font-size: 12px; font-weight: 400; line-height: 32px;}

.global .user  {position: absolute; left: 0; top: 10px;}

.global .util {position: absolute; right: 30px; top: 10px;}
.global .util ul li {position: relative; padding: 0 12px;}
.global .util ul li a {display: block;}

.head-search {position: absolute; bottom: 12px; right: -135px;}
.head-search .group {position: relative;}
.head-search .input {width: 150px; height: 30px; padding: 0 20px 0 0; font-size: 14px; border: 0; border-bottom: 1px soild #000; outline: none;}
.head-search .submit {display: block; position: absolute; right: 0; top: 0; width: 20px; height: 30px; border: 0; font-size: 0; line-height: 0; cursor
pointer; outline: none;}

.head {position: absolute; left: 0; top: 53px; width: 100%; max-height: 1000000px;}
.head .main-title {position: absolute; top: 50%; left: 0; margin-top: -32px; z-index: 10;}
.head img {border: 0; vertical-align: top; max-width: 100%;}
.head .nav {margin-left: 265px;}
.head ul {display: inline-block; vertical-align: top;}
.head .m1, .m2, .m3, .m4, .m5, .m6, .m7 {float: left; margin-left: 60px;}
.head .nav a {position: relative; display: block; height: 118px; font-size: 16px; font-weight: 500; line-height: 118px;}

padding-bottom: 120px;

위 코딩을 없애보고 넣어보고 했는데 달라지는 점이 없는데 샘플사이트에서는 위 코딩을 넣어놨는데

쓸데없는 코딩을 넣었을리는 없는데 위 코딩을 주석처리하거나 안하거나 변하는점이 없어서 저걸 왜 넣었는지를 모르겠습니다 혹시 아시는분 계시면 답변 부탁드려요