IE6上margin效果不一致 _HTML/CSS

IE6下margin效果不一致
这是一个导航菜单的CSS，在除IE6的其他版本下.lavaLampWithImage li a的margin设置为auto 12px是正常显示的，但是在IE6下margin显示过大，后面的菜单被挤到第二行了。只有把.lavaLampWithImage li a 的margin设置为auto 6px才能正常显示。。怎么解决这个问题呢？

CSS code


.lavaLampWithImage {
            position: relative;
            width: 930px;
            background: url("../img/bgTitle.png") no-repeat top;
            padding: 35px;
            margin: 0px 0;
            overflow: hidden;
        }
.lavaLampWithImage li {
                    float: left;
                    list-style: none;
                }
.lavaLampWithImage li.back {
                        background: url("../img/lava.gif") no-repeat right -30px;
                        top: 2px;
                        width: 9px; height: 30px;
                        z-index: 8;
                        position: absolute;
                    }
.lavaLampWithImage li.back .left {
                            background: url("../img/lava.gif") no-repeat top left;
                            height: 30px;
                            margin-right: 9px; /* 7px is the width of the rounded shape */
                        }
 .lavaLampWithImage li a {
                        font: bold 14px arial;
                        text-decoration: none;
                        color: #fff;
                        outline: none;
                        text-align: center;
                        top: -28px;
                        text-transform: uppercase;
                        letter-spacing: 0;
                        z-index: 10;
                        display: block;
                        float: left;
                        height: 30px;
                        position: relative;
                        overflow: hidden;
                        margin: auto 12px;    
                    }
.lavaLampWithImage li a:hover, .lavaLampWithImage li a:active, 

.lavaLampWithImage li a:visited {
                            border: none;
                        }

------解决方案--------------------
.lavaLampWithImage li a {
font: bold 14px arial;
text-decoration: none;
color: #fff;
outline: none;
text-align: center;
top: -28px;
text-transform: uppercase;
letter-spacing: 0;
z-index: 10;
display: block;
float: left;
height: 30px;
position: relative;
overflow: hidden;
margin: auto 12px;
_margin: auto 6px;/*加这行试试*/

}