resolution = screen.width;
if(resolution <= 800) {
    resolution = 800;
}else {
    resolution = 1024;
}
document.cookie = "resolution=" + resolution;
if (resolution <= 800) { 
    document.write('<link rel="stylesheet" type="text/css" href="squelettes/habillage_bis_800.css" />'); 
} else if (resolution <= 1024) {
    document.write('<link rel="stylesheet" type="text/css" href="squelettes/habillage_bis_1024.css" />');
}