IE6、IE7下的z-index问题
有html结构如下：

<div class="wrap">

		<div class="fl-wrap">

			left

		</div>

		<div class="fr-wrap">

			<ul>

				<li>

					<div class="fl">

						<div class="pmt-wrap">

							<a class="pmt">

								鼠标经过时，显示div

							</a>

							<div class="pmt-detail">

								...

							</div>

						</div>

					</div>

					<div class="fr">

						right

					</div>

					<div class="clear"></div>

				</li>

				<li>

					<div class="fl">

						<div class="pmt-wrap">

							<a class="pmt">

								鼠标经过时，显示div

							</a>

							<div class="pmt-detail hidden">

								...

							</div>

						</div>

					</div>

					<div class="fr">

						right

					</div>

					<div class="clear"></div>

				</li>

			</ul>

		</div>

		<div class="clear"></div>

	</div>

相关的css:

	.wrap{

		border:1px solid red;

		height:300px;

		padding:10px;

		width:500px;

	}

	.fl-wrap{

		border:1px solid green;

		float:left;

		height:100px;

		width:50px;

	}

	.fr-wrap{

		border:1px dashed blue;

		float:right;

		height:300px;

		width:440px;

	}

	ul{

		margin:0;

		padding:0;

	}

	.fr-wrap li{

		border:1px solid #000;

		height:100px;

		list-style-type:none;

		margin:5px;

		padding:5px;

		

	}

	.clear{

		clear:both;

		height:0;

		overflow:hidden;

	}

	.fr-wrap .fl{

		border:1px dashed red;

		float:left;

		height:100%;

		width:140px;

	}

	.fr-wrap .fr{

		border:1px dashed blue;

		float:right;

		height:100%;

		width:260px;

	}

	.fl .pmt-wrap{

		position:relative;

		*z-index:2;

	}

	.fl .pmt{

		cursor:pointer;

		font-size:12px;

		margin:5px;

		padding:0;

		position:relative;

		z-index:1;

	}

	.fl .pmt-detail{

		background-color:#fff;

		border:1px solid #ccc;

		height:200px;

		left:5px;

		position:absolute;

		top:16px;

		width:100px;

		z-index:3;

	}

	.hidden{

		display:none;

	}

火狐下的效果：（也是希望得到的效果）


IE6、IE7下的效果：