var res="";

if(screen.width > 640 && screen.width <= 800) { res = "800";} 
else {res=screen.width;}

if (res == 800 || res == 1024) {document.write("<link rel='stylesheet' type='text/css' href='/templates/design/de/style_800.css'>"); } 
else {document.write("<link rel='stylesheet' type='text/css' href='/templates/design/de/css_center.css'>"); }