function tariffs_winter() {
if (document.all)
var xMax = screen.width, yMax = screen.height;
else
if (document.layers)
var xMax = window.outerWidth, yMax = window.outerHeight;
else
var xMax = 1024, yMax=768;
var xOffset = (xMax - 800)/2, yOffset = (yMax - 600)/2;
window.open('tarifs_echo_des_montagnes.html','Tariffs',
'width=600,height=500,scrollbars=yes, resizable=yes, screenX='+xOffset+',screenY='+yOffset+',top='+yOffset+',left='+xOffset+'');
}