Merhabalar ;

kenzzofis.com adlı domaininde yaptığım e-ticaret çalısmasında orta alanla ilgili bir sıkıntım var

margin-left kullnarak ortalayabiliyorum fakat ekran çözünürlüğüne göre bu ayarlamam deişiyor Tüm ekran çözünürlüklerinde ortada nasıl çıkmasını sağlarım

yardımcı olabilirseniz sevinriim kodlar aşağıdadır.

index.php html çıktısı ->

<div style="margin-left:300px;float:left;">
  <div class="medium-title2">OKUL MOBİLYALARI</div>
  <div class="medium-r">    <div style="float:left; text-align:center">
        <div class="ilan"><a href="?kenzz=detay&altkat=29"><img src="urun_res/okulsira.jpg" height="80" width="108" /></a></div>
        <br style="clear:both" />
        <a href="?kenzz=detay&altkat=29" style="color:#000; text-decoration:none; font-size:11px">Okul Sıraları</a>
        </div>
            <div style="float:left; text-align:center">
        <div class="ilan"><a href="?kenzz=detay&altkat=30"><img src="urun_res/okulsira.jpg" height="80" width="108" /></a></div>
        <br style="clear:both" />
        <a href="?kenzz=detay&altkat=30" style="color:#000; text-decoration:none; font-size:11px">Çizim Masaları</a>
        </div>
            <div style="float:left; text-align:center">
        <div class="ilan"><a href="?kenzz=detay&altkat=31"><img src="urun_res/okulsira.jpg" height="80" width="108" /></a></div>
        <br style="clear:both" />
        <a href="?kenzz=detay&altkat=31" style="color:#000; text-decoration:none; font-size:11px">Panolar</a>
        </div>
            <div style="float:left; text-align:center">
        <div class="ilan"><a href="?kenzz=detay&altkat=32"><img src="urun_res/okulsira.jpg" height="80" width="108" /></a></div>
        <br style="clear:both" />
        <a href="?kenzz=detay&altkat=32" style="color:#000; text-decoration:none; font-size:11px">Yazı Tahtaları</a>
        </div>
            <div style="float:left; text-align:center">
        <div class="ilan"><a href="?kenzz=detay&altkat=33"><img src="urun_res/okulsira.jpg" height="80" width="108" /></a></div>
        <br style="clear:both" />
        <a href="?kenzz=detay&altkat=33" style="color:#000; text-decoration:none; font-size:11px">Bilgisayar Masaları</a>
        </div>
        <br style="clear:both" /></div></div><div style="margin-left:300px;float:left"><img src="dosyalar/medium-b.png" height="8" width="728"></div><br>
Css :
body, td, th {
	font-family: Arial, Helvetica, sans-serif;
	font-size: 12px;
}
body {
	background-color: #EEEEEE;
	margin: 0;
	padding: 0
}
.center {
	width: 980px;
	margin-left: auto;
	margin-right: auto;
	position: relative
}
.br {
	width:954px;
	background:url(images/br.png) no-repeat;
	height:15px;
	padding:13px;
	text-indent:85px;
	margin-top:5px
}
.cs p {
	margin:0;
	padding:0
}
	
.br a {
	font-size:12px;
	color:#333;
	text-decoration:none;
	margin-right:5px;
	margin-left:5px;
	

}
.br a:hover {
	color:#900
}
.top-menu {
	width: 980px;
	height: 65px;
	background: url(images/top-menu-background.png);
	position: relative;
	margin-top: 125px;
}
img {
	border: 0
}
.top {
	width: 100%;
	padding-top: 15px;
	padding-bottom: 15px;
	background-color: #000;
	position: relative
}
.top-inline {
	width: 980px;
	position: absolute;
	left: 50%;
	margin-left: -490px;
	top: 7px;
	color: #CCC
}
.top-inline a {
	color: #CCC;
	text-decoration: none;
	margin-left: 5px;
	margin-right: 5px
}
.top-inline a:hover {
	color: #F00
}
.menu-search {
	width: 335px;
	height: 43px;
	background: url(images/menu-search.png);
	position: absolute;
	left: 700px;
	top: 50px;
}
.menu-search form input {
	display: inline;
	margin-left: 40px;
	padding-top: 12px;
	padding-bottom: 12px;
	border: none;
	width: 235px;
	background: none
}
.menu-search img {
	position: absolute;
	right: 10px;
	top: 5px
}
.menu-links {
	position: absolute;
	top: 25px;
	left: 80px
}
.menu-links a {
	color: #CCC;
	text-decoration: none;
	font-size: 16px;
	margin-right: 15px
}
.menu-links a:hover {
	color: #F00
}
.top-banner {
	width: 468px;
	height: 60px;
	position: absolute;
	top: -90px;
	right: 0px;
	z-index: 9999;
	background-color:#666
}
.left {
	width:237px;
	float:left;
	margin-top:10px
}
.right {
	float:left;
	margin-top:10px;
}
.right2 {
	float:right;
	margin-left:15px;
	width:728px;
	margin-top:10px;
}

.small-title {
	width:237px;
	padding-top:27px;
	padding-bottom:28px;
	background:url(images/small.png);
	color:#FFF;
	text-indent:45px;
	font-size:14px;
	font-weight:bold
}
.small-r {
	width:217px;
	padding:10px;
	background:url(images/small-r.png) repeat-y
}
.anno {
	width:700px;
	padding-top:12px;
	padding-bottom:11px;
	padding-left:12px;
	padding-right:16px;
	background:url(images/top-anno.png);
	color:#FFF;
	font-size:16px;
	letter-spacing:0.5px
}
.anno a {
	font-weight:bold;
	color:#FFF
}
.left-banner {
	width:468px;
	height:250px;
	background-color:#333;
	float:left;
	margin-top:10px
}
.right-banner {
	width:250px;
	height:250px;
	margin-left:10px;
	margin-top:10px;
	float:left;
	background-color:#333
}
#kategoriler ul {
	width:230px;
	list-style-type:none ;
	margin:0;
	padding:0;
}
#kategoriler ul li {
	line-height:25px;
	text-indent:0px;
	font-size:14px;
	font-weight:bold;
}
#kategoriler ul li a {
	font-size:14px;
	font-weight:bold;
	color:#000;
	text-decoration:none;
	
}
#kategoriler ul li ul li {
	text-indent:25px;
}
#kategoriler ul li ul li a {
	display: block;
	line-height:27px;
	font-size:12px;
	font-weight:normal;
	text-decoration:none
}
#kategoriler ul li ul li a:hover {
	color:#F00
}
#kategoriler ul li a:hover {
	color:#F00
}
.medium-title {
	width:728px;
	padding-top:27px;
	padding-bottom:28px;
	background:url(images/medium.png);
	color:#FFF;
	text-indent:45px;
	font-size:14px;
	font-weight:bold;
}
.medium-title2 {
	width:728px;
	padding-top:27px;
	padding-bottom:28px;
	background:url(images/medium2.png);
	color:#FFF;
	text-indent:45px;
	font-size:14px;
	font-weight:bold;;
	position:relative
}
.medium-title3 {
	width:980px;
	padding-top:27px;
	padding-bottom:28px;
	background:url(images/medium3.png);
	color:#FFF;
	text-indent:45px;
	font-size:14px;
	font-weight:bold;
}

.medium-title2 a {
	position:absolute;
	right:10px;
	top:10px
}
.medium-r {
	width:708px;
	padding:10px;
	background:url(images/medium-r.png) repeat-y
}
.medium-r3 {
	width:960px;
	padding:10px;
	background:url(images/medium-r3.png) repeat-y
}
#uyeol p {
	margin:0;
	padding:0;
	margin-top:5px
}
#uyeol label[for=s] {
	float:left;
	width:125px;
	
	display: block;
	padding-left:0px
}
#uyeol span {
	color:#F00
}
#uyeol input[for=s], select {
	font-size:14pt;
	width:310px
}
#uyeol a {
	color:#F00;
	text-decoration:none
}
#cap {
	margin-left:122px
}
h2 {
	margin:0;
	padding:0;
	border-bottom:dotted 1px #ccc;
	font-size:16px;
	padding-bottom:7px;
	margin-bottom:10px
}
.butonlar {
	-moz-box-shadow:inset 0px 1px 0px 0px #f29c93;
	-webkit-box-shadow:inset 0px 1px 0px 0px #f29c93;
	box-shadow:inset 0px 1px 0px 0px #f29c93;
	background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #9e1000), color-stop(1, #ce0100) );
	background:-moz-linear-gradient( center top, #9e1000 5%, #ce0100 100% );
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#9e1000', endColorstr='#ce0100');
	background-color:#9e1000;
	-moz-border-radius:6px;
	-webkit-border-radius:6px;
	border-radius:6px;
	border:1px solid #d83526;
	display:inline-block;
	color:#ffffff;
	font-family:arial;
	font-size:15px;
	font-weight:bold;
	padding:6px 24px;
	text-decoration:none;
	text-shadow:1px 1px 0px #b23e35;
	cursor:pointer
}.butonlar:hover {
	background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #ce0100), color-stop(1, #9e1000) );
	background:-moz-linear-gradient( center top, #ce0100 5%, #9e1000 100% );
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#ce0100', endColorstr='#9e1000');
	background-color:#ce0100;
}.butonlar:active {
	position:relative;
	top:1px;
}

butonlar {
	-moz-box-shadow:inset 0px 1px 0px 0px #f29c93;
	-webkit-box-shadow:inset 0px 1px 0px 0px #f29c93;
	box-shadow:inset 0px 1px 0px 0px #f29c93;
	background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #9e1000), color-stop(1, #ce0100) );
	background:-moz-linear-gradient( center top, #9e1000 5%, #ce0100 100% );
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#9e1000', endColorstr='#ce0100');
	background-color:#9e1000;
	-moz-border-radius:6px;
	-webkit-border-radius:6px;
	border-radius:6px;
	border:1px solid #d83526;
	display:inline-block;
	color:#ffffff;
	font-family:arial;
	font-size:15px;
	font-weight:bold;
	padding:6px 24px;
	text-decoration:none;
	text-shadow:1px 1px 0px #b23e35;
	cursor:pointer
}.butonlar:hover {
	background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #ce0100), color-stop(1, #9e1000) );
	background:-moz-linear-gradient( center top, #ce0100 5%, #9e1000 100% );
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#ce0100', endColorstr='#9e1000');
	background-color:#ce0100;
}.butonlar:active {
	position:relative;
	top:1px;
}
.butonlar3 {
	-moz-box-shadow:inset 0px 1px 0px 0px #707070;
	-webkit-box-shadow:inset 0px 1px 0px 0px #707070;
	box-shadow:inset 0px 1px 0px 0px #707070;
	background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #9e9e9e), color-stop(1, #4d4d4d) );
	background:-moz-linear-gradient( center top, #9e9e9e 5%, #4d4d4d 100% );
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#9e9e9e', endColorstr='#4d4d4d');
	background-color:#9e9e9e;
	-moz-border-radius:6px;
	-webkit-border-radius:6px;
	border-radius:6px;
	border:1px solid #b3b3b3;
	display:inline-block;
	color:#ffffff;
	font-family:arial;
	font-size:16px;
	font-weight:bold;
	padding:6px 24px;
	text-decoration:none;
	text-shadow:1px 1px 0px #030303;
}.butonlar3:hover {
	background:-webkit-gradient( linear, left top, left bottom, color-stop(0.05, #4d4d4d), color-stop(1, #9e9e9e) );
	background:-moz-linear-gradient( center top, #4d4d4d 5%, #9e9e9e 100% );
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr='#4d4d4d', endColorstr='#9e9e9e');
	background-color:#4d4d4d;
}.butonlar3:active {
	position:relative;
	top:1px;
}
.ilan {
	width:110px;
	height:80px;
	text-align:center;
	float:left;
	margin-right:5px;
	margin-top:10px;
	text-align:center;
	font-size:11px;
	display:inline;
	border:solid 1px #d8d8d8
}
.ilan img {
	color:#333;
	margin-bottom:5px
}
.ilan a {
	color:#333;
	text-decoration:none
}
.ilan a:hover {
	color:#C00
}
.page {
	text-align:left
}
.page a {
	padding:4px;
	background-color:#C00;
	color:#FFF;
	text-decoration:none;
	margin-left:2px
}
.secenek {
	line-height:22px;
	border-bottom:solid 1px #ccc;
	background:url(images/arti.gif) no-repeat;
	background-position:right
}
.secenek a {
	color:#333;
	text-decoration:none;
	display:block
}
.sec {
	margin:0;
	padding:0
}
.logo {
	width:980px;
	left:50%;
	margin-left:-490px;
	position:absolute;
	top:40px
}
.tb1 {
	width:100px;
	padding-top:8px;
	padding-bottom:8px;
	background-color:#CCC;
	color:#333
}
.tb1 {
	float:left;
	width:100px;
	padding-top:8px;
	padding-bottom:8px;
	background-color:#333;
	color:#ffffff;
	margin-left:1px;
	font-weight:bold
}
.tb2 {
	float:left;
	width:297px;
	padding-top:8px;
	padding-bottom:8px;
	background-color:#333;
	color:#ffffff;
	margin-left:1px;
	font-weight:bold
}
.tb3 {
	float:left;
	width:100px;
	padding-top:8px;
	padding-bottom:8px;
	background-color:#333;
	color:#ffffff;
	margin-left:1px;
	font-weight:bold
}
.tb4 {
	float:left;
	width:100px;
	background-color:#333;
	color:#ffffff;
	margin-left:1px;
	font-weight:bold;
	padding-top:8px;
	padding-bottom:8px;
}
.tb5 {
	float:left;
	width:100px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc
}
.tb6 {
	float:left;
	width:297px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc;
	text-align:left;
	text-indent:5px
}
.tb7 {
	float:left;
	width:100px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc
}
.tb8 {
	float:left;
	width:100px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc;
}
.tb6 p, .tb7 p {
	margin:0;
	padding:0;
	margin-top:35px
}
.tb8 p {
	margin:0;
	padding:0;
	margin-top:5px
}


.tb5-2 {
	float:left;
	width:100px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc
}
.tb6-2 {
	float:left;
	width:555px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc;
	text-align:left;
	text-indent:5px
}
.tb7-2 {
	float:left;
	width:100px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc
}
.tb8-2 {
	float:left;
	width:100px;
	color:#333;
	margin-left:1px;
	height:80px;
	border-bottom:dotted 1px #ccc;
	text-align:center
}
.tb6-2 p, .tb7-2 p {
	margin:0;
	padding:0;
	margin-top:35px
}
.tb8-2 p {
	margin:0;
	padding:0;
	margin-top:5px
}


.bir {
	float:left;
	width:300px;
	background-color:#ffffff;
	
}
.iki {
	float:right;
	width:380px;
}
.l2 {
	width:150px;
	background-color:#EEEEEE;
	float:left;
	padding-top:5px;
	padding-bottom:5px;
	color:#333;
	text-indent:5px;
	margin-top:1px;
	font-weight:bold
}
.r2 {
	float:right;
	width:249px;
	background-color:#f5f5f5;
	padding-top:5px;
	padding-bottom:5px;
	color:#333;
	text-indent:5px;
	margin-top:1px
}
	
.res img {
  max-width: 500px;
  max-height: 350px;
  width: expression(this.width > 500 ? "500px" : true);
  height: expression(this.height > 350 ? "350px" : true);
  margin-top:30px;
  margin-bottom:30px
}
.mesaj {
	width:32px;
	height:32px;
	color:#FFF;
	font-weight:bold;
	background:url(images/oval.png) no-repeat;
	position:absolute;
	top:-15px;
	left:150px;
	text-align:center
}
.mesaj p {
	margin:0;
	padding:0;
	margin-top:9px
}
.odememesaj {
	width:32px;
	height:32px;
	color:#FFF;
	font-weight:bold;
	background:url(images/oval.png) no-repeat;
	position:absolute;
	top:-15px;
	left:528px;
	text-align:center
}
.odememesaj p {
	margin:0;
	padding:0;
	margin-top:9px
}
.footer-top {
	width:980px;
	margin-left:auto;
	margin-right:auto;
	height:17px;
	background:url(images/footer-top.png) no-repeat;
	margin-top:15px
}
.footer-bottom {
	width:980px;
	margin-left:auto;
	margin-right:auto;
	height:17px;
	background:url(images/footerbottom.png) no-repeat
}
.footer-repeat {
	width:960px;
	padding:10px;
	margin-left:auto;
	margin-right:auto;
	padding-top:0;
	padding-bottom:0;
	background:url(images/footer-repeat.png) repeat-y;
	font-size:11px

}
.footer-repeat a {
	color:#000;
	text-decoration:none;
	margin-left:5px;
	margin-right:5px;
	font-weight:bold
}
.footer-repeat a:hover {
	color:#C00;
}
.detayblok {
	float: left;
	width: 670px;
	margin-top: 5px;
	margin-bottom: 10px;
	margin-left: 35px;
	border: 1px solid #E6E6E6;
	background-color:#FFF;
}
.detaybaslik {
	font-family: Geneva, sans-serif;
	font-size: 14px;
	font-weight: bold;
	color: #003366;
	float: left;
	height: 30px;
	width: 600px;
	margin-bottom: 5px;
	border-bottom-width: 3px;
	border-bottom-style: solid;
	border-bottom-color: #F30;
	margin-top: 7px;
	margin-left: 45px;
}
.detaybaslik1 {
	font-family: Geneva, sans-serif;
	font-size: 19px;
	font-weight: bold;
	color: #390;
	float: left;
	height: 30px;
	width: 600px;
	margin-bottom: 5px;
	border-bottom-width: 3px;
	border-bottom-style: solid;
	border-bottom-color: #F30;
	margin-top: 15px;
	margin-left: 45px;
}
.detayaciklama {
	float: left;
	width: 625px;
	margin-top: 7px;
	margin-bottom: 7px;
	margin-left: 25px;
	font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;
	font-size: 13px;
	color: #333;
	text-decoration: none;
}
.detaydahil {
	font-family: Geneva, sans-serif;
	font-size: 14px;
	color: #333;
	display: block;
	float: left;
	width: 400px;
	list-style-position: outside;
	list-style-type: none;
	list-style-image: url(../images/li-ico.png);
}

.detayimaj {
	float: left;
	width: 670px;
	margin-top: 5px;
}
.div_texbox {
	width:347px;
	float:right;
	background-color:#E6E6E6;
	height:35px;
	margin-top:3px;
	padding-top:5px;
	padding-bottom:3px;
	padding-left:5px;
}

.textbox {
	background-image: url(../images/16t.png);
	background-color:#FFFFFF;
	background-repeat: no-repeat;
	background-position:left;
	width:285px;
	font:normal 18px Arial;
	color: #999999;
	padding:3px 5px 3px 19px;
}
.textbox:focus, .textbox:hover {
	background-color:#F0FFE6;
}

.username {
    	background-image: url(../images/16m.png);
    	background-repeat: no-repeat;
    	background-position:left;
    	background-color:#FFFFFF;
	width:285px;
    	font:normal 18px Arial;
    	color: #999999;
    	padding:3px 5px 3px 19px;
}
.username:focus, .username:hover {
	background-color:#F0FFE6;
}
   
.password {
    	background-image: url(../images/16s.png);
    	background-repeat: no-repeat;
   	background-position:left;
   	background-color:#FFFFFF;
	width:285px;
    	font:normal 18px Arial;
    	color: #999999;
    	padding:3px 5px 3px 19px;
}
.password:focus, .password:hover {
	background-color:#F0FFE6;
}

.button_div {
	width:287px;
	float:right;
	background-color:#fff;
	border:1px solid #ccc;
	text-align:right;
	height:35px;
	margin-top:3px;
	padding:5px 32px 3px;
}
.buttons {
	background: #e3e3db;
	font-size:12px; 
	color: #989070; 
	padding: 6px 14px;
	border-width: 2px;
	border-style: solid;
	border-color: #fff #d8d8d0 #d8d8d0 #fff;
	text-decoration: none;
	text-transform:uppercase;
	font-weight:bold;
}

/* VELVET */