how can i do this style sheet cross browser



body {
text-align:center;
font-family: trebuchet ms, sans-serif;
margin-top:30px;
margin-bottom:30px;
}
#wrapper {
width:800px;
margin:20px;
}
.my_main {
width:800px;
background-color:#000066;
color:#ffffff;
font-size:16px;
border:20px solid #f0f0f0;
text-align:left;
margin-left:90px;
}

.left_col {
width:350px;
float:left;
}
.left_menu {
width:350px;
border-top:10px solid #ff6600;
}
.left_menu a:link,.left_menu a:visited {
border-bottom:5px solid #000080;
display:block;
padding:4px;
width:350px;
padding-left:6px;
text-decoration:none;
color:#ffffff;
}
.left_menu a:hover {
color:#ffffff;
width:350px;
background-color:#ff6600;
}
.main_col {
width:350px;
padding:10px;
float:right;
background-color:#000066;
color:#ffffff;
}