function if_opera(url){
    if(is_opera()){
        AddCss(url)
    }
}
function is_opera(version, param){
    if (version == null){
      var version = '';
    }
    var agt = navigator.userAgent.toLowerCase();
    if (param == null){
        return (agt.indexOf("opera "+version) != -1 || agt.indexOf("opera/"+version) != -1);
    } else {
        var vers = parseInt(agt.charAt(agt.indexOf("Opera")+7));
        if (param == 'gte'){
            return (vers >= version);
        }
        else if (param == 'gt'){
            return (vers > version);
        }
        else if (param == 'lte'){
            return (vers <= version);
        }
        else if (param == 'lt'){
            return (vers < version);
        }
    }
}
function AddCss(url){
    var l=document.createElement("link");
    l.setAttribute("type","text/css");
    l.setAttribute("rel","stylesheet");
    l.setAttribute("href",url);
    document.getElementsByTagName("head")[0].appendChild(l);
}