Pure CSS vertical menu on the left with a rounding error / layout: 3 columns - header

CSS for a vertical menu on the left with a rounding problem for Mozilla (before revision 1.8b4)

#zone_left dl{
margin:-5px;
padding:0;
}
#zone_left dt{
margin:1px;
padding:0;
}
#zone_left dt a{
background-color:#D2E1FB;
border-left:.5em solid #E8F0FD;
border-right:.5em solid #E8F0FD;
color:#0A00B0;
display:block;
/*padding:4px 3px 5px 5px;*/
line-height:1.7em;/*rounding errors with Mozilla*/
text-decoration:none;
font-weight:800;
width:8.9em;
}

/* start IE_Mac hide\*/
* html #zone_left dt a{
width:10em; /*value for MSIE 5*/
}
* html #zone_left dt a/**/{
width/**/:100%; /*value for MSIE 5.5*/
width:/**/8.9em; /*value for MSIE 6*/
}
/* end IE_Mac hide*/

#zone_left dt a:hover{
background-color:#A9CFFE;
border-right:.5em solid #000;
/*border-left:.5em solid #E8F0FD;*/
color:#FFF;
}

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CSS / 3 columns / header / footer