function extractEssentiel(){

ie = (document.all) ? 1:0
ns = (document.layers) ? 1:0

if (ie || ns) window.open("lessentiel.htm","ESSENTIEL","directory=no,location=no,menubar=no,resizable=no,scrollbars=no,status=no,toolbar=no,width=300,height=100");
else alert('Netscape Navigator 4, Microsoft Internet Explorer 4 ou superieur necessaire...');

}