var browser = '';
var linkPart1 = '<link rel="stylesheet" href="/main/css_1_';
var linkPart2 = '.css" />';
if (navigator.appName.indexOf('Microsoft')>=0) { browser = 'ie'; } 
else if (navigator.appName.indexOf('Netscape')>=0) browser = 'ns';
else browser = 'ie';
document.write(linkPart1+browser+linkPart2);