Browser sniffing or detection : Conditional Css

<!--[if gt IE 6]>
<link rel="stylesheet" type="text/css" href="css/ie7fix.css" media="screen" />

<![endif]-->
<!--[if lte IE 6]>
<link rel="stylesheet" type="text/css" href="css/ie6fix.css" media="screen" /> 

<![endif]-->

<script language="Javascript" >

    var useragent = navigator.userAgent;
    var bName = (useragent.indexOf('Firefox') > -1) ? 'Firefox' :
navigator.appName;


    if (bName == "Firefox") 
    {
        
        document.writeln('<style> #nav_bar_t6 {padding-left:33px;
padding-right:33px; } #footer {margin-left:18%}</style>');
    }

    if(navigator.userAgent.indexOf ("Netscape")!=-1)
    {
        
        document.writeln('<style> #nav_bar_t4 {WIDTH:
14.2%;padding-left:2px;} #footer {margin-left:18%}</style>');
    }
    
    if(navigator.userAgent.indexOf ("Opera")!=-1)
    {
        document.writeln('<style> #nav_bar_t6 {padding-left:38px;
padding-right:33px;} #footer {margin-left:18%}</style>');
    }
</script>