ie6 =         (parseFloat(navigator.appVersion.split("MSIE")[1]) != 6) ? false : true;
ie7 =         (parseFloat(navigator.appVersion.split("MSIE")[1]) != 7) ? false : true;
ie8 =         (parseFloat(navigator.appVersion.split("MSIE")[1]) != 8) ? false : true;
opera =       (navigator.userAgent.indexOf("Opera")  ==-1) ? false : true;

var head = document.getElementsByTagName('head')[0];
function loadCSS () {
    link = document.getElementById('cssLink');
    
    if (ie6) {                    
        link.href = 'css/naniIE6.css'
    } else if (ie7) {                        
        link.href = 'css/naniIE7.css'
    } else if (ie8) {    
    } else if (opera) {            
        link.href = 'naniOpera.css'
    }
}

loadCSS();