var Win=(navigator.userAgent.indexOf("Win")!=-1);
var Mac=(navigator.userAgent.indexOf("Mac")!=-1);
var Explorer=(navigator.appName.indexOf("Explorer")!=-1);
var Netscape=(navigator.appName.indexOf("Netscape")!=-1);
var Version=navigator.appVersion.charAt(0);

if 
(Win && Explorer && Version=="4")
{document.write('<LINK rel="stylesheet" type="text/css" href="/style_winIE.css">');}

else if
(Win && Netscape && Version=="5")
{document.write('<LINK rel="stylesheet" type="text/css" href="/style_winIE.css">');}

else if
(Win && Netscape && Version=="4")
{document.write('<LINK rel="stylesheet" type="text/css" href="/style_winNS.css">');}

else if
(Explorer && Mac && Version=="4")
{document.write('<LINK rel="stylesheet" type="text/css" href="/style_macIE.css">');}

else if
(Mac && Netscape && Version=="5")
{document.write('<LINK rel="stylesheet" type="text/css" href="/style_macNS.css">');}

else if
(Mac && Netscape && Version=="4")
{document.write('<LINK rel="stylesheet" type="text/css" href="/style_macNS.css">');}