图片放大效果的话，建议用一个额外的 div层放置放大后的图片，这样布局就不会乱了。鼠标放上去就显示这个层。
.img2{
/*这里写你的所有图片都会用到的样式*/
}
.img2:first-child, .img2:last-child{
/*这里写第一个图片和最后一个图片会用到的样式*/
}
.img1:hover .showBigImg{
display:block
}
对于这个大图的div层的显示，可以稍加js控制，这样就可以所有图片共用一个div层来放置大图。
希望能帮助到你
[HTML部分]<div id="tbody">
<span class="txt_1">横向的JS相册效果</span>
<div id="mainbody">
<img src="images/01.jpg" alt="横向JS相册" width="640" height="400" id="mainphoto" rel="images/01.jpg" name="#" />
</div>
<img src="images/goleft.gif" width="11" height="56" id="goleft" />
<img src="images/goright.gif" width="11" height="56" id="goright" />
<div id="photos">
<div id="showArea">
<!--src: 缩略图地址 rel: 大图地址 name: 网址 -->
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/02.jpg" alt="横向JS相册" width="80" height="50" rel="images/02.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/02.jpg" alt="横向JS相册" width="80" height="50" rel="images/02.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/02.jpg" alt="横向JS相册" width="80" height="50" rel="images/02.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/02.jpg" alt="横向JS相册" width="80" height="50" rel="images/02.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
<img src="images/02.jpg" alt="横向JS相册" width="80" height="50" rel="images/02.jpg" name="#" />
<img src="images/01.jpg" alt="横向JS相册" width="80" height="50" rel="images/01.jpg" name="#" />
</div>
</div>
</div>
[CSS部分]
body {background:#000margin:0font:12px Verdanatext-align:center}
#tbody {width:650pxmargin:20px autotext-align:left}
#mainbody {width:640pxmargin:5pxborder:1px solid #222padding:1px}
#mainphoto {cursor:pointerdisplay:block}
#goleft {float:leftclear:leftmargin:6px 5px 0 3px}
#goright {float:rightclear:rightmargin:6px 3px 0 5px}
#photos {width:610pxheight:54pxline-height:54pxborder:1px solid #222margin:10px 0overflow:hidden}
#showArea img {display:blockfloat:leftmargin:1px 0cursor:pointerborder:1px solid #222}.txt_1 {font:bold 24px Verdana, Tahomacolor:#fff}
[JS部分]
<script language="javascript" type="text/javascript">
var browse = window.navigator.appName.toLowerCase()
var MyMar
var speed = 1//速度，越大越慢
var spec = 1//每次滚动的间距, 越大滚动越快
var minOpa = 90//滤镜最小值
var maxOpa = 100//滤镜最大值
var spa = 2//缩略图区域补充数值
var w = 0
spec = (browse.indexOf("microsoft") >-1) ? spec : ((browse.indexOf("opera") >-1) ? spec*10 : spec*20)
function $(e) {return document.getElementById(e)}
function goleft() {$('photos').scrollLeft -= spec}
function goright() {$('photos').scrollLeft += spec}
function setOpacity(e, n) {
if (browse.indexOf("microsoft") >-1) e.style.filter = 'alpha(opacity=' + n + ')'
else e.style.opacity = n/100
}
$('goleft').style.cursor = 'pointer'
$('goright').style.cursor = 'pointer'
$('mainphoto').onmouseover = function() {setOpacity(this, maxOpa)}
$('mainphoto').onmouseout = function() {setOpacity(this, minOpa)}
$('mainphoto').onclick = function() {location = this.getAttribute('name')}
$('goleft').onmouseover = function() {this.src = 'images/goleft2.gif'MyMar=setInterval(goleft, speed)}
$('goleft').onmouseout = function() {this.src = 'images/goleft.gif'clearInterval(MyMar)}
$('goright').onmouseover = function() {this.src = 'images/goright2.gif'MyMar=setInterval(goright,speed)}
$('goright').onmouseout = function() {this.src = 'images/goright.gif'clearInterval(MyMar)}
window.onload = function() {
setOpacity($('mainphoto'), minOpa)
var rHtml = ''
var p = $('showArea').getElementsByTagName('img')
for (var i=0i<p.lengthi++) {
w += parseInt(p[i].getAttribute('width')) + spa
setOpacity(p[i], minOpa)
p[i].onclick = function() {location = this.getAttribute('name')}
p[i].onmouseover = function() {
setOpacity(this, maxOpa)
$('mainphoto').src = this.getAttribute('rel')
$('mainphoto').setAttribute('name', this.getAttribute('name'))
setOpacity($('mainphoto'), maxOpa)
}
p[i].onmouseout = function() {
setOpacity(this, minOpa)
setOpacity($('mainphoto'), minOpa)
}
rHtml += '<img src="' + p[i].getAttribute('rel') + '" width="0" height="0" alt="" />'
}
$('showArea').style.width = parseInt(w) + 'px'
var rLoad = document.createElement("div")
$('photos').appendChild(rLoad)
rLoad.style.width = "1px"
rLoad.style.height = "1px"
rLoad.style.overflow = "hidden"
rLoad.innerHTML = rHtml
}
</script>
