if (window.screen){
  var w = screen.width;
  css800 = "sidemtreestyle.css";
  css1024 = "sidemtreestyle1.css";
  if(w>=740 & w<835){
    document.write("<link rel='stylesheet' href='" + css800 + "' type='text/css'>");
  }
  if(w>=835){
    document.write("<link rel='stylesheet' href='" + css1024 + "' type='text/css'>");
  }
}