我这个CSS为啥IE6和IE7不支持啊(有代码)

IE8,火狐和谷歌都可以,但是IE6和IE7不行,代码如下:
CSS部分:
HTML code:

*
{

}

/* =Basic HTML, Non-essential
----------------------------------------------------------------------*/

a
{
text-decoration: none;
}

body
{

}

h1
{
background: inherit;
color: #933;
font: 17px Georgia, serif;
text-align: center;
}

p
{
clear: both;
font: 10px Verdana, sans-serif;
text-align: center;
}

p a
{
background: inherit;
color: #777;
}

p a:hover
{
background: inherit;
color: #000;
}

/* =Hoverbox Code
----------------------------------------------------------------------*/

.hoverbox
{
cursor: default;
list-style: none;
}

.hoverbox a
{
cursor: default;
}

.hoverbox a .preview
{
display: none;
}

.hoverbox a:hover .preview
{
display: block;
position: absolute;
top: -33px;
left: -45px;
z-index: 1;
}

.hoverbox img
{
background: #fff;
border-color: #aaa #ccc #ddd #bbb;
border-style: solid;
color: inherit;
vertical-align: top;
width: 253px;
height: 49px;
}

.hoverbox li
{
background: #eee;
border-color: #ddd #bbb #aaa #ccc;
border-style: solid;
border-width: 0px;
color: inherit;
display: inline;
float: left;
margin: 0px;