var hasard=Math.random();
if(hasard>=0 && hasard<0.2)
window.location="b.htm";
if(hasard>=0.2 && hasard<0.5)
window.location="a.htm";
if(hasard>=0.5 && hasard<0.7)
window.location="d.htm";
if(hasard>=0.7 && hasard<0.8)
window.location="e.htm";
if(hasard>=0.8 && hasard<=1)
window.location="c.htm";