if(screen.width >= 1024)
 document.write("<link rel='stylesheet' href='../css/main_b.css'>"); 
else
 document.write("<link rel='stylesheet' href='../css/main.css'>");

function NeuFenster(d,f,w,h,sc)
{
    optio=("width="+w+",height="+h+",scrollbars="+sc+",locationbar=no,menubar=no,status=no");
    MeinFenster=window.open("",f,optio);
     MeinFenster.location=d;
    MeinFenster.focus();
}