var d, dom, ie, ie4, ie5x, moz, mac, win, lin, old, ie5mac, ie5xwin, op;

d = document;
n = navigator;
na = n.appVersion;
nua = n.userAgent;
win = ( na.indexOf( 'Win' )!= -1 );
mac = ( na.indexOf( 'Mac' )!= -1 );
lin = ( na.indexOf( 'Linux' )!= -1 );

if (!d.layers ){
dom = ( d.getElementById );
op = ( nua.indexOf( 'Opera' )!= -1 );
konq = ( nua.indexOf( 'Konqueror' )!= -1 );
saf = ( nua.indexOf( 'Safari' )!= -1 );
moz = ( nua.indexOf( 'Gecko' )!= -1 );
ie = ( d.all &&!op );
ie4 = ( ie &&!dom );

ie5x = ( d.all && dom );
ie5mac = ( mac && ie5x );
ie5xwin = ( win && ie5x );
} 

if (ie){
  document.write('<link href="css/pruebaGPRS.css" rel="stylesheet" type="text/css">');
//  alert("es ie");
  }
else{
  document.write('<link href="css/pruebaGPRSn.css" rel="stylesheet" type="text/css">');
  //alert("es net");
  }