aleksandr8i,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
ul{
margin:0 auto;
width:350px;
}
li{
float:left;
width:50px;
list-style:none;
}
li:hover{
background:#00FF00;
}
li:nth-child(n +5):hover{
background:#FF3333;
}
</style>
</head>
<body> <ul>
<li class="bg_link">link</li>
<li class="bg_link">link</li>
<li class="bg_link">link</li>
<li class="bg_link">link</li>
<li class="bg_link">link</li>
<li class="bg_link">link</li>
<li class="bg_link">link</li>
</ul>
</body>
</html>